Polymerisable compounds and the use thereof in liquid-crystal media and liquid-crystal displays

ABSTRACT

The present invention relates to polymerizable compounds, to processes and intermediates for the preparation thereof, to the use thereof for optical, electro-optical and electronic purposes, in particular in liquid-crystal (LC) media and LC displays having a polymer-stabilized blue phase, and in LC media for LC displays of the PS or PSA type (“polymer sustained” or “polymer sustained alignment”), and to LC media and LC displays comprising these compounds.

The present invention relates to polymerisable compounds, to processesand intermediates for the preparation thereof, to the use thereof foroptical, electro-optical and electronic purposes, in particular inliquid-crystal (LC) media and LC displays having a polymer-stabilisedblue phase, and in LC media for LC displays of the PS or PSA type(“polymer sustained” or “polymer sustained alignment”), and to LC mediaand LC displays comprising these compounds.

Media for display elements which operate in the liquid-crystalline bluephase (blue phase for short) are known from the prior art. Such displaysare described, for example, in WO 2004/046805 A1 and WO 2008/061606 A1.

The blue phase is generally observed at the transition from the nematicstate to the optically isotropic state. The medium in theliquid-crystalline blue phase may be blue, as the name suggests, butalso colourless. The aim of efforts to date was to extend thetemperature range of the blue phase from less than one degree to a rangewhich is useful in practice (cf. H. Kikuchi et al., Nature Materials(2002), 1(1), 64-68; Kikuchi, H. et al., Polymeric Materials Science andEngineering, (2003), 89, 90-91).

For this purpose, it has been proposed in the prior art to add apolymerisable compound to the LC medium, and then to polymerise thiscompound in situ in the LC medium. The polymer or polymer network formedin the process is claimed to stabilise the blue phase.

The polymer-stabilised blue phases described to date in the prior artuse, for example, a monoreactive non-mesogenic monomer together with adireactive mesogenic monomer as monomers.

WO 2005/080529 A1 describes, for example, polymer-stabilised blue phasescomprising mono- and multireactive monomers.

The present invention was based on the object of finding suitablemonomers and corresponding polymers for the stabilisation of bluephases. The polymer is intended, in particular, to have the followingeffects on the properties of the stabilised LC phase:

-   -   broad temperature range of the blue phase,    -   fast response time,    -   small clearing-point difference on polymerisation,    -   low operating voltage (V_(op)),    -   small variation of the operating voltage with temperature,    -   low hysteresis of the transmission of a cell when the operating        voltage is changed in order to achieve defined grey shades.

In addition, monomers which have a good “voltage holding ratio” (VHR),have high clearing points, and are stable to exposure to light andtemperature are required. Good solubility in LC materials or goodmiscibility with the LC medium is furthermore necessary in order toachieve a good distribution in the LC medium.

The present invention is thus based on the object of providing improvedpolymerisable compounds, and LC media comprising such compounds, inparticular for use in LC displays having a polymer-stabilised bluephase. The polymerisable compounds according to the invention areintended to stabilise the blue phase. The LC media according to theinvention are intended to have one or more improved properties, inparticular selected from the properties mentioned above. In particular,the LC media are intended to have a broad blue phase, enable fastswitching, have a good voltage holding ratio (VHR), require low voltages(V_(op)) for the switching process and exhibit low hysteresis (ΔV) andhave a low memory effect (ME). The LC media are intended to be stable toexposure to light and temperature.

Furthermore, so-called PS and PSA (“polymer sustained” and “polymersustained alignment” respectively) displays, for which the term “polymerstabilised” is also occasionally used, are known from the prior art. Inthese displays, a small amount (for example 0.3% by weight, typically<1% by weight) of one or more polymerisable compound(s) is added to theLC medium and, after introduction into the LC cell, is polymerised orcrosslinked in situ, usually by UV photopolymerisation, with or withoutan applied electrical voltage between the electrodes. The addition ofpolymerisable mesogenic or liquid-crystalline compounds, also known asreactive mesogens or “RMs”, to the LC mixture has proven particularlysuitable.

The term “PSA” is used below, unless indicated otherwise, asrepresentative of PS displays and PSA displays.

In the meantime, the PS(A) principle is being used in diverse classicalLC displays. Thus, for example, PSA-VA, PSA-OCB, PSA-IPS, PSA-FFS andPSA-TN displays are known. The polymerisation of the polymerisablecompound(s) is preferably carried out with an applied electrical voltagein the case of PSA-VA and PSA-OCB displays and with or without anapplied electrical voltage in the case of PSA-IPS displays. As can beshown in test cells, the PS(A) method results in a pretilt in the cell.In the case of PSA-OCB displays, for example, the bend structure can bestabilised, so that an offset voltage is unnecessary or can be reduced.In the case of PSA-VA displays, the pretilt has a positive effect on theresponse times. For PSA-VA displays, a standard MVA or PVA pixel andelectrode layout can be used. In addition, however, only one structuredelectrode side and no protrusions, for example, are also sufficient,which significantly simplifies production and at the same time resultsin very good contrast at the same time as very good light transmission.

PSA-VA displays are described, for example, in JP 10-036847 A, EP 1 170626 A2, U.S. Pat. No. 6,861,107, U.S. Pat. No. 7,169,449, US2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PSA-OCBdisplays are described, for example, in T.-J-Chen et al., Jpn. J. Appl.Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C— Chien, Jpn. J. Appl.Phys. 43, 2004, 7643-7647. PSA-IPS displays are described, for example,in U.S. Pat. No. 6,177,972 and Appl. Phys. Lett. 1999, 75(21), 3264.PSA-TN displays are described, for example, in Optics Express 2004,12(7), 1221.

PSA displays, like the conventional LC displays described above, can beoperated as active-matrix or passive-matrix displays. In the case ofactive-matrix displays, individual pixels are usually addressed byintegrated, non-linear, active elements, such as, for example,transistors (for example thin-film transistors or “TFTs”), while in thecase of passive-matrix displays, the addressing is usually carried outby the multiplex method, both methods being known from the prior art.

However, not all combinations consisting of LC mixture and polymerisablecomponent are suitable for PSA displays, since, for example, aninadequate tilt, or none at all, is established or since, for example,the so-called “voltage holding ratio” (VHR or HR) is inadequate for TFTdisplay applications. In addition, it has been found that the LCmixtures and RMs known from the prior art still have some disadvantageson use in PSA displays. Thus, not every known RM which is soluble in LCmixtures is suitable for use in PSA displays.

In addition, the selected combination of LC host mixture/RM should havethe lowest possible rotational viscosity and the best possibleelectrical properties. In particular, it should have the highestpossible VHR. In PSA displays, a high VHR after irradiation with UVlight is particularly necessary since UV exposure is a necessary part ofthe display production process, but also occurs as normal exposureduring operation of the finished display.

In particular, it would be desirable to have available novel materialsfor PSA displays which generate a particularly low pretilt angle.Preference is given here to materials which generate a lower pretiltangle during polymerisation for the same exposure time than thematerials known to date, and/or whose use enables the (higher) pretiltangle that can be achieved with the known materials to be achievedalready after a shorter exposure time. It was thus possible for theproduction time (“tact time”) of the display to be shortened and for thecosts of the production process to be reduced.

A further problem in the production of PSA displays is the presence orremoval of residual amounts of unpolymerised RMs, in particular afterthe polymerisation step for generation of the pretilt angle in thedisplay. For example, unreacted RMs of this type may adversely affectthe properties of the display by polymerising in an uncontrolled manner,for example during operation after completion of the display.

Thus, the PSA displays known from the prior art often exhibit theundesired effect of so-called “image sticking” or “image burn”, i.e. theimage produced in the LC display by temporary addressing of individualpixels still remains visible even after the electric field in thesepixels has been switched off, or after other pixels have been addressed.

It is therefore desirable for the polymerisation of the RMs duringproduction of the PSA display to proceed as completely as possible andfor the presence of unpolymerised RMs in the display to be excluded asfar as possible or reduced to a minimum. To this end, materials whichenable the most effective and complete polymerisation possible arerequired.

There is thus still a great demand for PSA displays and LC media andpolymerisable compounds for use in such displays, which do not exhibitthe disadvantages described above or only do so to a small extent andhave improved properties. In addition, there is a great demand for PSAdisplays, and materials for use in PSA displays, which have advantageousproperties, in particular facilitate a high specific resistance at thesame time as a large working-temperature range, short response times,even at low temperatures, and a low threshold voltage, a low pretiltangle, a multiplicity of grey shades, high contrast and a broad viewingangle, and high values of the voltage holding ratio (VHR) after UVexposure and low-temperature stability, also known as LTS, i.e. thestability of the LC mixture to individual components spontaneouslycrystallising out.

The invention is thus based on the further object of providing novelsuitable materials, in particular RMs and LC media comprising thelatter, for use in PSA displays which do not have the disadvantagesindicated above, or only do so to a reduced extent, polymerise asquickly and completely as possible, enable a low pretilt angle to beestablished as quickly as possible, reduce or prevent the occurrence ofimage sticking in the display, and preferably at the same time enablevery high specific resistance values, low threshold voltages and shortresponse times. In addition, the LC media should have favourable LCphase properties and high VHR and LTS values.

The objects described above have been achieved in accordance with theinvention by the provision of materials, processes and LC displays asdescribed in the present application. In particular, it has been found,surprisingly, that the objects described above can be achieved in partor full by using LC media which comprise one or more polymerisablecompounds according to the invention, as described above, for theproduction of such LC displays or by providing LC displays having a bluephase or PSA displays which contain one or more compounds according tothe invention in polymerised form.

The polymerisable compounds according to the invention contain a centralmesogenic group and at least two polymerisable groups which are linkedto the mesogenic group directly or via spacer groups, where the centralmesogenic group consists of three cyclic radicals which are linked toone another by two ethylene bridges.

The use of the polymerisable compounds according to the invention in LCmedia according to the invention for LC displays having apolymer-stabilised blue phase results in significant stabilisation ofthe blue phase. In addition, it has been found, surprisingly, that asignificant reduction in hysteresis (ΔV₅₀) and an increase in contrastare achieved on use of the polymerisable compounds according to theinvention in LC media having a polymer-stabilised blue phase, comparedwith polymerisable compounds and LC media as described in the prior art.

In PSA displays, the use of the polymerisable compounds according to theinvention in LC media according to the invention results in the desiredpretilt being achieved particularly quickly and in significantlyshortened times in production of the display.

The prior art, such as, for example, U.S. Pat. No. 7,440,160 (WO2004/046805 A1) and the documents cited therein, describes LC media forLC display elements which operate in the liquid-crystalline blue phase(blue phase for short). WO 2005/080529 A1 describes polymer-stabilisedblue phases comprising mono- and multireactive monomers. US 2009/0267025A1 (WO 2006/063662 A1), US 2009/051855 A1, US 2009/0059132 A1 and US2009/0059157 A1 describe the polymer stabilisation of blue phasescomprising liquid-crystalline reactive components (also known asreactive mesogens, “RMs” for short). In the publications mentionedabove, however, preference is given to the use of RMs containing phenylradicals either linked directly or via ester groups, such as, forexample, the following two RMs:

in which x denotes either 3 or 6.

WO 2008/061606 A1 describes RMs containing a mesogenic group consistingof directly linked cyclohexyl rings, and the use thereof for the polymerstabilisation of blue phases. This also mentions, inter alia, theoptional use of additional comonomers, which can be selected, interalia, from a list which also contains a formula RM27 for an RMcontaining three phenyl radicals linked via ethyl bridges. However, WO2008/061606 A1 does not disclose any specific examples in whichcomonomers of this type were used. Neither are the advantagessurprisingly achieved using such compounds, as described above and belowfor the LC media of the present invention, suggested therein.

In particular, the monomers presented in the present invention are moresuitable than the ester-bridged substances presented in WO 2008/061606A1 for stabilising the initial state of the LC medium, so that a verygood black state is achieved after switching off. In addition, themonomers presented in the present invention are distinguished by asimpler synthesis and—apart from the reactive groups—by greater chemicalstability.

WO 93/22397 A1 describes an electro-optical system comprising a PDLCfilm. This describes, for example, compounds of the following genericformula which contain three phenyl radicals linked via ethyl bridges:

whereY² can denote H₂C═CHCOO—, H₂C═CMeCOO— or CH₂═CH— andV² can denote O or a single bond andn can denote an integer between 2 and 12 and

can denote an optionally fluorinated 1,4-phenylene unit.

Furthermore, the synthesis of the following compound is describedexplicitly in Example 1

However, no properties of this compound on use in an LC display aredisclosed.

In addition, the use of these such compounds for the stabilisation ofblue phases or in PSA displays is neither described nor suggested in WO93/22397 A1.

PDLC displays are fundamentally completely different from the LCdisplays of the present invention. Thus, PDLC displays consist of aphase-separated system, where droplets of a low-molecular-weight LCmedium are embedded in a polymer matrix. Light scattering occurs at thephase boundaries. By matching the refractive indices of the LC phase andthe polymer phase and by re-aligning the LC molecules in the droplets inan electric field, the display can be switched between alight-scattering state and a transparent state. This requires, interalia, careful choice of the LC media and polymer materials in order toensure matching of the refractive indices, and the use of a large amountof polymer material in order to form the polymer matrix. In addition,PDLC displays usually have worse electro-optical properties, such as,for example, slow response times and strong viewing-angle dependence ofthe contrast, and disadvantages caused by the design, such as complexproduction, low long-term stability and high layer thickness, and aretherefore not suitable for more modern applications, such as, forexample, in flat-panel screens for TV sets or notebooks.

In contrast to PDLC displays, the type and amount of the polymerisablecompounds in the LC displays according to the invention having a bluephase and PSA displays are selected in such a way that nomacroscopically evident phase boundaries with significant lightscattering occur between the polymer and LC medium. Accordingly, thechoice of suitable LC media and polymerisable compounds for LC displaysaccording to the invention is made in accordance with different criteriathan for PDLC displays. Thus, the polymerisable component should havethe highest possible solubility in the LC medium and should only be usedin very small amounts, for example, in the case of PSA displays. Precisematching of the refractive indices as in PDLC displays is, by contrast,normally not necessary. Considerably greater requirements are also madeof the polymerisation properties of the polymerisable component, asdescribed above. In addition, the LC media must meet significantlyhigher requirements with respect to the electro-optical properties andmust have, for example, particularly fast response times, highresistance values and low operating and threshold voltages.

EP 0 648 827 A1 describes reactive liquid crystals of a broad genericformula, which may contain, inter alia, a mesogenic group of thefollowing formula:

in which L¹ and L² denote CN or W²—C_(r)H_(s)F_(2r+s−1), W² denotes asingle bond, O, S or CO, r denotes 1 or 2, and s denotes 0, 1, 2, 3, 4or 5. Furthermore, the use of reactive liquid crystals of this type inelectro-optical scattering systems or for the preparation of aligned LCpolymers is described therein. However, specific compounds containing amesogenic group of this type are not specifically disclosed. Inaddition, the use of these or other reactive liquid crystals for thepolymer stabilisation of blue phases is neither described nor suggested.

U.S. Pat. No. 7,070,838 describes polymerisable compounds of a broadgeneric formula in which the mesogenic group contains a phenyl radicalwhich is substituted by fluorinated methyl, in particular for use inoptical LC polymer films. Polymerisable compounds of a formula BRM-15and of a formula BRM-b-5 containing three phenyl radicals linked viaethyl bridges are also disclosed therein, as is a mixture ofpolymerisable liquid crystals comprising a compound of this type.Furthermore, the use of such compounds in mixtures consisting ofpolymerisable compounds together with chiral components is mentioned.However, use in low-molecular-weight LC media or LC media having a bluephase is neither disclosed nor suggested.

US 2003/0203128 A1 describes polymerisable compounds of a broad genericformula in which the mesogenic group contains a central fluoreneradical, in particular for use in optical LC polymer films.Polymerisable compounds of the formula 67-70 in which the fluoreneradical is linked to two adjacent phenyl radicals via ethyl bridges arealso disclosed therein, as is a mixture of polymerisable liquid crystalscomprising this compound.

Furthermore, the use of such compounds in mixtures consisting ofpolymerisable compounds together with chiral components is mentioned.However, use in low-molecular-weight LC media or LC media having a bluephase is neither disclosed nor suggested.

Thus, the prior art neither describes nor suggests polymer-stabilisedblue phases for LC media having a reactive component which preferablyconsists of polymerisable compounds according to the invention.

The invention relates to the use of compounds of the formula IP^(a)-(Sp^(a))_(s1)-A²-CH₂CH₂-A¹-CH₂CH₂-A³-(Sp^(b))_(s2)-P^(b)  Iin which the individual radicals have the following meaning

-   P^(a), P^(b) each, independently of one another, denote a    polymerisable group,-   Sp^(a), Sp^(b) on each occurrence, identically or differently,    denote a spacer group,-   s1, s2 each, independently of one another, denote 0 or 1,-   A¹, A², A³ each, independently of one another, denote a radical    selected from the following groups    -   a) the group consisting of trans-1,4-cyclohexylene,        1,4-cyclohexenylene and 4,4′-bicyclohexylene, in which, in        addition, one or more non-adjacent CH₂ groups may be replaced by        —O— and/or —S— and in which, in addition, one or more H atoms        may be replaced by F,    -   b) the group consisting of 1,4-phenylene and 1,3-phenylene, in        which, in addition, one or two CH groups may be replaced by N        and in which, in addition, one or more H atoms may be replaced        by L,    -   c) the group consisting of tetrahydropyran-2,5-diyl,        1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl,        cyclobut-1,3-diyl, piperidine-1,4-diyl, thiophene-2,5-diyl and        selenophene-2,5-diyl, each of which may, in addition, be mono-        or polysubstituted by L,    -   d) the group consisting of saturated, partially unsaturated or        fully unsaturated, and optionally substituted, polycyclic        radicals having 5 to 20 cyclic C atoms, one or more of which may        also be replaced by heteroatoms, preferably selected from the        group consisting of bicyclo[1.1.1]pentane-1,3-diyl,        bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl,

-   -    where, in addition, one or more H atoms in these radicals may        be replaced by L, and/or one or more double bonds may be        replaced by single bonds, and/or one or more CH groups may be        replaced by N,

-   L on each occurrence, identically or differently, denotes F, Cl, CN,    SCN, SF₅ or straight-chain or branched, in each case optionally    fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,

-   R⁰, R⁰⁰ each, independently of one another, denote H, F or    straight-chain or branched alkyl having 1 to 12 C atoms, in which,    in addition, one or more H atoms may be replaced by F,

-   M denotes —O—, —S—, —CH₂—, —CHY¹— or —CY¹Y²—,

-   Y¹, and Y² each, independently of one another, have one of the    meanings indicated above for R⁰, or denote Cl or CN, and preferably    denote H, F, Cl, CN, OCF₃ or CF₃,    or a polymer obtainable by polymerisation of one or more compounds    of the formula I, in LC displays having a blue phase or in LC    displays of the PS or PSA type.

The invention furthermore relates to an LC medium comprising one or morecompounds of the formula I and optionally additionally one or morepolymerisable compounds.

The invention furthermore relates to an LC medium comprising one or morecompounds of the formula I and one or more additional compounds, whichmay also be mesogenic, liquid-crystalline and/or polymerisable.

The invention furthermore relates to an LC medium comprising a polymerobtainable by polymerisation of one or more compounds of the formula I,and optionally comprising one or more additional compounds, which mayalso be mesogenic, liquid-crystalline and/or polymerisable.

The invention furthermore relates to an LC medium comprising

-   -   a polymerisable component comprising one or more polymerisable        compounds of the formula I, or the polymerised form of this        polymerisable component, and    -   a liquid-crystalline component, also referred to below as “LC        host mixture”, comprising one or more, preferably two or more,        low-molecular-weight (i.e. monomeric and unpolymerisable)        compounds as described above and below, which are preferably        mesogenic or liquid-crystalline.

The invention furthermore relates to the use of LC media comprising oneor more compounds of the formula I in LC displays having a blue phase orin LC displays of the PS or PSA type.

The invention furthermore relates to a process for the preparation of anLC medium as described above and below in which one or morelow-molecular-weight liquid-crystalline compounds, or an LC host mixtureas described above and below, are mixed with one or more compounds ofthe formula I and optionally with further liquid-crystalline compoundsand/or additives.

The invention furthermore relates to the use of compounds of the formulaI and LC media according to the invention comprising them in LC displaysfor stabilisation of the blue phase, in particular over the greatestpossible temperature range.

The invention furthermore relates to the use of compounds of the formulaI and LC media according to the invention comprising them in PS and PSAdisplays for the generation of a tilt angle in the LC medium by in-situpolymerisation of the compound(s) of the formula I in the PSA display,preferably with application of an electric or magnetic field.

The invention furthermore relates to an LC display containing one ormore compounds of the formula I or an LC medium according to theinvention, in particular a PS or PSA display, particularly preferably adisplay having a blue phase, a PSA-VA, PSA-OCB, PSA-IPS, PSA-FFS orPSA-TN display.

The invention furthermore relates to an LC display of the PS or PSA typecontaining an LC cell having two substrates and two electrodes, where atleast one substrate is transparent to light and at least one substratehas one or two electrodes, and a layer, located between the substrates,of an LC medium comprising a polymerised component and alow-molecular-weight component, where the polymerised component isobtainable by polymerisation of one or more polymerisable compoundsbetween the substrates of the LC cell in the LC medium, preferably withapplication of an electrical voltage to the electrodes, characterised inthat at least one of the polymerisable compounds is selected fromformula I.

The invention furthermore relates to a process for the production of anLC display as described above and below in which an LC medium comprisingone or more low-molecular-weight liquid-crystalline compounds or an LChost mixture as described above and below and one or more polymerisablecompounds, at least one of which is selected from formula I, isintroduced into an LC cell having two substrates and two electrodes asdescribed above and below, and the polymerisable compounds arepolymerised, preferably with application of an electrical voltage to theelectrodes.

The PS and PSA displays according to the invention have two electrodes,preferably in the form of transparent layers, which are applied to oneor both of the substrates which form the LC cell. Either in each caseone electrode is applied to each of the two substrates, as, for example,in PSA-VA, PSA-OCB or PSA-TN displays according to the invention, orboth electrodes are applied to only one of the two substrates, while theother substrate has no electrode, as, for example, in PSA-IPS or PSA-FFSdisplays according to the invention.

The invention furthermore relates to novel compounds of the formula I,to processes for the preparation thereof, and to novel intermediatesused in or obtained from these processes, in particular compounds of theformula I, and sub-formulae thereof as defined above and below, in whichone or more of the radicals A¹, A² and A³ are selected from the group d)as defined in formula I, consisting of optionally substituted, saturatedor partially or fully unsaturated, polycyclic radicals having 5 to 20cyclic C atoms, one or more of which may also be replaced byheteroatoms.

Particular preference is given to an LC medium, an LC display, a processor a use as described above and below in which the LC medium or thepolymerisable or polymerised component present therein does not compriseany compounds of the following formula:

in which P^(a), P^(b), Sp^(a), Sp^(b), s1, s2 and L r have the meaningsindicated above and below, r denotes 0, 1, 2, 3 or 4, and Z^(a) andZ^(b) each, independently of one another, denote —COO— or —OCO—.

The following meanings apply above and below:

The term “cyclic C atom” denotes a C atom which forms a carbo- orheterocyclic radical with other C atoms and/or heteroatoms.

The terms “tilt” and “tilt angle” relate to a tilted alignment of the LCmolecules of an LC medium relative to the surfaces of the cell in an LCdisplay (here preferably a PS or PSA display). The tilt angle heredenotes the average angle (<90°) between the longitudinal molecular axesof the LC molecules (LC director) and the surface of the plane-parallelouter plates which form the LC cell. A low value for the tilt angle(i.e. a large deviation from the 90° angle) corresponds to a large tilthere. A suitable method for measurement of the tilt angle is given inthe examples. Unless indicated otherwise, tilt angle values disclosedabove and below relate to this measurement method.

The term “mesogenic group” is known to the person skilled in the art andis described in the literature, and denotes a group which, due to theanisotropy of its attracting and repelling interactions, essentiallycontributes to causing a liquid-crystal (LC) phase inlow-molecular-weight or polymeric substances. Compounds containingmesogenic groups (mesogenic compounds) do not necessarily have to havean LC phase themselves. It is also possible for mesogenic compounds toexhibit LC phase behaviour only after mixing with other compounds and/orafter polymerisation. Typical mesogenic groups are, for example, rigidrod- or disc-shaped units. An overview of the terms and definitions usedin connection with mesogenic or LC compounds is given in Pure Appl.Chem. 73(5), 888 (2001) and C. Tschierske, G. Pelzl, S. Diele, Angew.Chem. 2004, 116, 6340-6368.

The term “spacer group” or “spacer”, also referred to as “Sp” above andbelow, is known to the person skilled in the art and is described in theliterature see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C.Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.Unless indicated otherwise, the term “spacer group” or “spacer” aboveand below denotes a flexible group which connects the mesogenic groupand the polymerisable group(s) to one another in a polymerisablemesogenic compound.

The term “reactive mesogen” or “RM” denotes a compound containing onemesogenic group and one or more functional groups which are suitable forpolymerisation (also referred to as polymerisable group or group P).

The terms “low-molecular-weight compound” and “unpolymerisable compound”denote compounds, usually monomeric, which contain no functional groupwhich is suitable for polymerisation under the usual conditions known tothe person skilled in the art, in particular under the conditions usedfor the polymerisation of RMs.

“Halogen” denotes F, Cl, Br or I.

Definitions such as “alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms” etc., meanthat the radicals containing a carbonyl group (CO) and the unsaturatedradicals, such as alkenyl and alkynyl, have at least two C atoms, andthe branched radicals have at least three C atoms.

The polymerisable group P^(a,b) is a group which is suitable for apolymerisation reaction, such as, for example, free-radical or ionicchain polymerisation, polyaddition or polycondensation, or for apolymer-analogous reaction, for example addition or condensation onto amain polymer chain. Particular preference is given to groups for chainpolymerisation, in particular those containing a C═C double bond or—C≡C— triple bond, and groups which are suitable for polymerisation withring opening, such as, for example, oxetane or epoxide groups.

Preferred groups P^(a,b) are selected from the group consisting ofCH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k3)—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—,(CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—,HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN— and W⁴W⁵W⁶Si—,in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 Catoms, in particular H, F, C₁ or CH₃, W² and W³ each, independently ofone another, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionallysubstituted by one or more radicals L as defined above which are otherthan P-Sp-, k₁, k₂ and k₃ each, independently of one another, denote 0or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Particularly preferred groups P^(a,b) are selected from the groupconsisting of CH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—O—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,(CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—,(CH₂═CH—CH₂)₂N—CO—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH— and W⁴W⁵W⁶Si—, in which W¹denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, inparticular H, F, Cl or CH₃, W² and W³ each, independently of oneanother, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, k₁, k₂ and k₃ each,independently of one another, denote 0 or 1, k₃ preferably denotes 1,and k₄ denotes an integer from 1 to 10.

Very particularly preferred groups P^(a,b) are selected from the groupconsisting of CH₂═CW¹—CO—O—, in particular CH₂═CH—CO—O—,CH₂═C(CH₃)—CO—O— and CH₂═CF—CO—O—, furthermore CH₂═CH—O—,(CH₂═CH)₂CH—O—CO—, (CH₂═CH)₂CH—O—,

Further very particularly preferred groups P^(a,b) are selected from thegroup consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate,chloroacrylate, oxetane and epoxide groups, and particularly preferablydenote an acrylate or methacrylate group.

Preferred spacer groups Sp^(a,b) are selected from the formula Sp″-X″,so that the radical P^(a/b)-Sp^(a/b)- conforms to the formulaP^(a/b)-Sp″-X″—, where

-   Sp″ denotes alkylene having 1 to 20, preferably 1 to 12, C atoms,    which is optionally mono- or polysubstituted by F, Cl, Br, I or CN,    and in which, in addition, one or more non-adjacent CH₂ groups may    each be replaced, independently of one another, by —O—, —S—, —NH—,    —N(R⁰)—, —Si(R⁰⁰R⁰⁰⁰)—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —S—CO—,    —CO—S—, —N(R⁰⁰)—CO—O—, —O—CO—N(R⁰⁰)—, —N(R⁰⁰)—CO—N(R⁰⁰)—, —CH═CH— or    —C≡C— in such a way that O and/or S atoms are not linked directly to    one another,-   X″ denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N(R⁰⁰)—,    —N(R⁰⁰)—CO—, —N(R⁰⁰)—CO—N(R⁰⁰)—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,    —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,    —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY²═CY³—, —C≡C—, —CH═CH—CO—O—,    —O—CO—CH═CH— or a single bond,-   R⁰⁰ and R⁰⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms, and-   Y² and Y³ each, independently of one another, denote H, F, Cl or CN.-   X′ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—,    —NR⁰—CO—, —NR⁰—CO—NR⁰— or a single bond.

Typical spacer groups Sp″ are, for example, —(CH₂)_(p1)—,—(CH₂CH₂O)_(q1)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰⁰R⁰⁰⁰—O)_(p1)—, in which p1 is an integer from 1 to 12, q1 is aninteger from 1 to 3, and R⁰⁰ and R⁰⁰⁰ have the meanings indicated above.

Particularly preferred groups -Sp″—X″— are —(CH₂)_(p1)—, —(CH₂)_(p1)—O—,—(CH₂)_(p1)—O—CO—, —(CH₂)_(p1)—O—CO—O—, in which p1 and q1 have themeanings indicated above.

Particularly preferred groups Sp″ are, for example, in each casestraight-chain ethylene, propylene, butylene, pentylene, hexylene,heptylene, octylene, nonylene, decylene, undecylene, dodecylene,octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene,ethenylene, propenylene and butenylene.

In a further preferred embodiment of the invention, P^(a) and/or P^(b)in formula I denote a radical containing two or more polymerisablegroups (multifunctional polymerisable radicals). Suitable radicals ofthis type and polymerisable compounds containing them and thepreparation thereof are described, for example, in U.S. Pat. No.7,060,200 B1 or US 2006/0172090 A1. Particular preference is given tomultifunctional polymerisable radicals selected from the followingformulae:—X-alkyl-CHP¹—CH₂—CH₂P²  I*a—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂P³  I*b—X-alkyl-CHP¹CHP²—CH₂P³  I*c—X-alkyl-C(CH₂P¹)(CH₂P²)—C_(aa)H_(2aa+1)  I*d—X-alkyl-CHP¹—CH₂P²  I*e—X-alkyl-CHP¹P²  I*f—X-alkyl-CP¹P²—C_(aa)H_(2aa+1)  I*g—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂OCH₂—C(CH₂P³)(CH₂P⁴)CH₂P⁵  I*h—X-alkyl-CH((CH₂)_(aa)P¹)((CH₂)_(bb)P²)  I*1—X-alkyl-CHP¹CHP²—C_(aa)H_(2aa+1)  I*k—X′-alkyl-C(CH₃)(CH₂P¹)(CH₂P²)  I*min which

-   alkyl denotes a single bond or straight-chain or branched alkylene    having 1 to 12 C atoms, in which one or more non-adjacent CH₂ groups    may each be replaced, independently of one another, by    —C(R⁰⁰)═C(R⁰⁰⁰)—, —C≡C—, —N(R⁰⁰)—, —O—, —S—, —CO—, —CO—O—, —O—CO—,    —O—CO—O— in such a way that O and/or S atoms are not linked directly    to one another, and in which, in addition, one or more H atoms may    be replaced by F, Cl or CN, where R⁰⁰ and R⁰⁰⁰ have the meanings    indicated above,-   aa and bb each, independently of one another, denote 0, 1, 2, 3, 4,    5 or 6,-   X has one of the meanings indicated for X′, and-   P¹⁻⁵ each, independently of one another, have one of the meanings    indicated for P^(a).

Preferred radicals A¹ in formula I are selected from the groupconsisting of the following formulae:

in which the individual rings may also additionally be mono- orpolysubstituted by L as described above and below.

A¹ very particularly preferably denotes a radical selected from thegroup consisting of the following formulae:

Preferred radicals A² and A³ in formula I are selected from the groupconsisting of the following formulae:

in which the individual rings may also additionally be mono- orpolysubstituted by L as described above and below.

Particularly preferred radicals A² and A³ are selected from the groupconsisting of the following formulae:

very particularly preferably

Further particularly preferred radicals A² and A³ are selected from thegroup consisting of the following formulae:

Further particularly preferred compounds of the formula I andsub-formulae thereof indicated above and below are those in which

-   -   s1 and s2 each denote 0,    -   s1 and s2 each denote 1,    -   s1 denotes 1 and s2 denotes 0 or s1 denotes 0 and s2 denotes 1.

Very particularly preferred compounds of the formula I are selected fromthe group consisting of the following formulae:

in which L has on each occurrence, identically or differently, one ofthe meanings indicated above and below, r denotes 0, 1, 2, 3 or 4, and ndenotes an integer between 1 and 24, preferably between 1 and 12, veryparticularly preferably between 2 and 8, and in which, if a radical isnot mentioned at the end of a single or double bond, it is a terminalCH₃ or CH₂ group.

In the formulae I1-I80,

preferably denotes a group selected from the group consisting of thefollowing formulae:

P^(a) and P^(b) in the compounds of the formula I and sub-formulaethereof preferably denote acrylate or methacrylate, furthermorefluoroacrylate.

Sp^(a) and Sp^(b) in the compounds of the formula I and sub-formulaethereof preferably denote a radical selected from the group consistingof —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO—O— or—(CH₂)_(p1)—O—CO—O— and mirror images thereof, in which p1 denotes aninteger from 1 to 12, preferably from 1 to 6, particularly preferably 1,2 or 3, where these groups are linked to P^(a) or P^(b) in such a waythat O atoms are not directly adjacent.

The invention furthermore relates to novel compounds of the formula IP^(a)-(Sp^(a))_(s1)-A²-CH₂CH₂-A¹-CH₂CH₂-A³-(Sp^(b))_(s2)—P^(b)  Iin which P^(a), P^(b), Sp^(a), Sp^(b), s1, s2, A¹, A² and A³ have themeaning indicated above and below, andin which one or more of the radicals A¹, A² and A³ are selected from thegroup d) consisting of saturated, partially saturated or fullyunsaturated, and optionally substituted, polycyclic radicals having 5 to20 cyclic C atoms, one or more of which may also be replaced byheteroatoms,preferably in which one or more of the radicals A¹, A² and A³ areselected from the group consisting of bicyclo[1.1.1]pentane-1,3-diyl,bicyclo[2.2.2]-octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl,

where, in addition, one or more H atoms in these radicals may bereplaced by L, and/or one or more double bonds may be replaced by singlebonds, and/or one or more CH groups may be replaced by N, where L, R⁰,R⁰⁰, M, Y¹ and Y² have the meaning indicated in formula I.

The invention furthermore relates to LC media and LC displays, inparticular those in accordance with the refinements and preferredembodiments, and all combinations thereof as described above and belowwhich comprise one or more novel compounds of the formula I.

Of these novel compounds, particular preference is given to those inwhich

-   -   the radicals from group d) are selected from group d1)        consisting of

where, in addition, one or more H atoms in these radicals may bereplaced by L as defined in formula I, where L particularly preferablydenotes F, CN, SCN, SF₅, CH₂F, CHF₂, CF₃, OCH₂F, OCHF₂ or OCF₃,

-   -   the radicals from group d) are selected from group d2)        consisting of

where, in addition, one or more H atoms in these radicals may bereplaced by L as defined in formula I, where L particularly preferablydenotes F, CN, SCN, SF₅, CH₂F, CHF₂, CF₃, OCH₂F, OCHF₂ or OCF₃,

-   -   the radicals P^(a) and P^(b) are selected from the group        consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate,        chloroacrylate, oxetane and epoxide groups, particularly        preferably acrylate or methacrylate groups,    -   the radicals Sp^(a) and Sp^(b) are selected from the group        consisting of —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO—        and —(CH₂)_(p1)—O—CO—O— and mirror images thereof, in which p1        denotes an integer from 1 to 12, preferably from 1 to 6,        particularly preferably 1, 2 or 3, and where these radicals are        linked to P^(a) or P^(b) in such a way that O atoms are not        directly adjacent,    -   s1 and s2 each denote 0,    -   s1 and s2 each denote 1,    -   s1 denotes 1 and s2 denotes 0 or s1 denotes 0 and s2 denotes 1.

Of these novel compounds, very particular preference is given to thoseselected from one or more of the following groups:

the group consisting of the formulae I9-I16,

the group consisting of the formulae I23-I28,

the group consisting of the formulae I37-I44,

the group consisting of the formulae I49-I54,

the group consisting of the formulae I63-I70 and

the group consisting of the formulae I75-I80,

in which L has one of the meanings indicated above and below, and n isan integer between 1 and 24, preferably between 1 and 12, veryparticularly preferably between 2 and 8.

The invention furthermore relates to novel intermediates for thepreparation of compounds of the formula I, selected from formula IAG-O-(Sp^(a))_(s1)-A²-CH₂CH₂-A¹-CH₂CH₂-A³-(Sp^(b))_(s2)-O-G′  IAin which A¹, A², A³, Sp^(a), Sp^(b), s1 and s2 have the meaningsindicated in formula I or sub-formulae thereof, or one of the preferredmeanings indicated above and below, and G and G′ each, independently ofone another, denote an H atom or a protecting group.

Suitable protecting groups G are known to the person skilled in the art.Preferred protecting groups are alkyl, acyl and alkylsilyl or arylsilylgroups, 2-tetrahydropyranyl or methoxymethyl.

The compounds and intermediates of the formulae I and IA andsub-formulae thereof can be prepared analogously to processes known tothe person skilled in the art and described in standard works of organicchemistry, such as, for example, in Houben-Weyl, Methoden derorganischen Chemie [Methods of Organic Chemistry], Thieme-Verlag,Stuttgart.

Particularly suitable and preferred processes for the preparation ofcompounds and intermediates of the formulae I and IA and sub-formulaethereof are depicted by way of example in the following schemes andpreferably contain one or more of the steps described below.

The compounds of the formula I are preferably prepared fromcorresponding dialdehydes 1. These are reacted with suitabletriphenylphosphonium salts in a Wittig reaction. Scheme 1 describes thisby way of example for the reaction with thepara-bromobenzyltriphenylphosphonium salts 2. The latter are furthermoreparticularly suitable as reactants for subsequently yielding compoundscontaining the preferred spacer groups Sp=(CH₂)_(p1).

Firstly, the compounds 3 are obtained from the dialdehydes 1 and thebenzyltriphenylphosphonium salts 2 in a Wittig reaction. These compounds3 are then reacted directly with, for example, alkynols 4 in aSonogashira reaction to give the compounds 5. In the subsequenthydrogenation, the ethylene bridges and the alkyl spacers are obtainedsimultaneously. The compounds 6 can then be esterified, for exampleusing acrylic acid derivatives. In this way, the particularly preferredpolymerisable compounds I (for example compounds 7) of the acrylate ormethacrylate type are obtained.

The person skilled in the art will be able to modify the synthesis in asuitable manner and thus obtain further compounds of type I. Theparticularly preferred compounds containing an alkoxy spacer orcontaining acrylates bonded directly to the ring are obtained, forexample, using p-methoxybenzyltriphenylphosphonium salts 8 (cf. Scheme2). After the Wittig reaction, the compounds 9 are obtained. These arehydrogenated to the compounds 10. The cleavage of the methoxy groups canbe carried out by reaction with hydrobromic acid in glacial acetic acidor with BBr₃. The bisphenols 11 can then be converted directly intopolymerisable compounds I (for example compounds 12).

The particularly preferred compounds containing an alkoxy spacer areobtained from the compounds 11 by reaction with, for example,bromoalkanols 13 (cf. Scheme 3). The compounds 13 obtained are thenesterified, for example using acrylic acid derivatives.

For the production of PSA displays according to the invention, thepolymerisable compounds are polymerised or crosslinked (if one compoundcontains two or more polymerisable groups) by in-situ polymerisation inthe LC medium between the substrates of the LC display with applicationof a voltage. The polymerisation can be carried out in one step. It isalso possible firstly to carry out the polymerisation with applicationof a voltage in a first step in order to generate a pretilt angle, andsubsequently, in a second polymerisation step without an appliedvoltage, to polymerise or crosslink the compounds which have not reactedin the first step (“end curing”).

Suitable and preferred polymerisation methods are, for example, thermalor photopolymerisation, preferably photopolymerisation, in particular UVphotopolymerisation. One or more initiators can optionally also be addedhere. Suitable conditions for the polymerisation and suitable types andamounts of initiators are known to the person skilled in the art and aredescribed in the literature. Suitable for free-radical polymerisationare, for example, the commercially available photoinitiatorsIrgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocure1173®(Ciba AG). If an initiator is employed, its proportion is preferably0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.

The polymerisable compounds according to the invention are also suitablefor polymerisation without an initiator, which is accompanied byconsiderable advantages, such as, for example, lower material costs andin particular less contamination of the LC medium by possible residualamounts of the initiator or degradation products thereof. Thepolymerisation can thus also be carried out without the addition of aninitiator. In a preferred embodiment, the LC medium thus comprises nopolymerisation initiator.

The polymerisable component or the LC medium may also comprise one ormore stabilisers in order to prevent undesired spontaneouspolymerisation of the RMs, for example during storage or transport.Suitable types and amounts of stabilisers are known to the personskilled in the art and are described in the literature. Particularlysuitable are, for example, the commercially available stabilisers fromthe Irganox® series (Ciba AG), such as, for example, Irganox® 1076. Ifstabilisers are employed, their proportion, based on the total amount ofRMs or the polymerisable component, is preferably 10-10,000 ppm,particularly preferably 50-500 ppm.

The polymerisable compounds according to the invention can bepolymerised individually, but it is also possible to polymerise mixtureswhich comprise two or more polymerisable compounds according to theinvention, or mixtures comprising one or more polymerisable compoundsaccording to the invention and one or more further polymerisablecompounds (comonomers), which are preferably mesogenic orliquid-crystalline. In the case of polymerisation of such mixtures,copolymers form. The invention furthermore relates to the polymerisablemixtures mentioned above and below. The polymerisable compounds andcomonomers are mesogenic or non-mesogenic, preferably mesogenic orliquid-crystalline.

Suitable and preferred comonomers for use in displays according to theinvention are selected, for example, from the following formulae:

in which the individual radicals have the following meanings:

-   P¹ and P² each, independently of one another, denote a polymerisable    group, preferably having one of the meanings indicated above and    below for P, particularly preferably an acrylate, methacrylate,    fluoroacrylate, oxetane, vinyloxy or epoxide group,-   Sp¹ and Sp² each, independently of one another, denote a single bond    or a spacer group, preferably having one of the meanings indicated    above and below for Sp^(a), particularly preferably —(CH₂)_(p1)—,    —(CH₂)_(p1)—O—, —(CH₂)_(p1)—CO—O— or —(CH₂)_(p1)—O—CO—O—, in which    p1 is an integer from 1 to 12, and where the linking to the adjacent    ring in the last-mentioned groups takes place via the O atom,-   where, in addition, one or more of the radicals P¹-Sp¹- and P²-Sp²-    may denote a radical R^(aa), with the proviso that at least one of    the radicals P¹-Sp¹- and P²-Sp²- present does not denote R^(aa),-   R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkyl    having 1 to 25 C atoms, in which, in addition, one or more    non-adjacent CH₂ groups may each be replaced, independently of one    another, by C(R⁰)═C(R⁰⁰)—, —CO—, —≡C—, —N(R⁰)—, —O—, —S—, —CO—,    —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not    linked directly to one another and in which, in addition, one or    more H atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly    preferably straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl or alkylcarbonyloxy having 1 to 12 C atoms (where the    alkenyl and alkynyl radicals have at least two C atoms and the    branched radicals have at least three C atoms),-   R⁰, R⁰⁰ each, independently of one another and identically or    differently on each occurrence, denote H or alkyl having 1 to 12 C    atoms,-   R^(y) and R^(z) each, independently of one another, denote H, F, CH₃    or CF₃,-   Z¹ denotes —O—, —CO—, —C(R^(y)R^(z))— or —CF₂CF₂—,-   Z² and Z³ each, independently of one another, denote —CO—O—, —O—CO—,    —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —(CH₂)_(n)—, where n is 2, 3 or 4,-   L on each occurrence, identically or differently, denotes F, Cl, CN,    SCN, SF₅ or straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12    C atoms, preferably F,-   L′ and L″ each, independently of one another, denote H, F or Cl,-   r denotes 0, 1, 2, 3 or 4,-   s denotes 0, 1, 2 or 3,-   t denotes 0, 1 or 2,-   x denotes 0 or 1.

In addition to the compounds of the formula I or IA, the LC medium orthe polymerisable component preferably comprises one or more compoundsselected from the group consisting of the formulae M16-M29, particularlypreferably consisting of the formulae M16-M21, very particularlypreferably consisting of the formulae M16, M17 and M18.

The LC medium or the polymerisable component preferably comprises nocompounds of the formula M10 in which Z² and Z³ denote —COO— or —OCO—.

Besides the polymerisable compounds described above, the LC media foruse in the LC displays according to the invention comprise an LC mixture(“host mixture”) comprising one or more, preferably two or more,low-molecular-weight (i.e. monomeric or unpolymerised) compounds. Thelatter are stable or unreactive to a polymerisation reaction under theconditions used for polymerisation of the polymerisable compounds. Inprinciple, any LC mixture which is suitable for use in conventional VAand OCB displays is suitable as host mixture.

Suitable LC mixtures are known to the person skilled in the art and aredescribed in the literature. LC media for VA displays are described inEP 1 378 557 A1. LC media for OCB displays are described in EP 1 306 418A1 and DE 102 24 046 A1. LC media for LC displays having a blue phaseare described in WO 2006/063662 A1 and the documents cited therein.

Particularly preferred LC media for use in LC displays having a bluephase are described below:

An LC medium according to the invention having a blue phase preferablycomprises

-   -   a polymerisable component A, preferably in a concentration of 1        to 25%, particularly preferably 2 to 20%, very particularly        preferably 3 to 15%, comprising, preferably consisting        principally of, very particularly preferably consisting        exclusively of, one or more compounds of the formula I and        optionally one or more additional polymerisable compounds, and    -   a liquid-crystalline component B comprising one or more,        preferably two or more, low-molecular-weight (i.e. monomeric and        unpolymerisable) compounds, preferably in a concentration of        20-100%, preferably having positive dielectric anisotropy,        preferably consisting principally of, very particularly        preferably consisting exclusively of, one or more compounds of        the formula II

-   -   in which the individual radicals have the following meaning    -   R²² denotes H, F, Cl, CN, NCS, SF₅, SO₂CF₃ or straight-chain or        branched alkyl having 1 to 20 C atoms, which is unsubstituted or        mono- or polysubstituted by F, Cl or CN, and in which, in        addition, one or more non-adjacent CH₂ groups may also each be        replaced, independently of one another, by —O—, —S—, —NH—,        —NR⁰¹—, —SiR⁰¹R⁰²—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—,        —CY⁰¹═CY⁰¹— or —C≡C— in such a way that O and/or S atoms are not        linked directly to one another,    -   Y⁰¹, Y⁰² each, independently of one another, denote F, Cl or CN,        the radicals Y⁰¹ and Y⁰² also denote H,    -   R⁰¹, R⁰² each, independently of one another, denote H or alkyl        having 1 to 12 C atoms,    -   A²¹, A²², A²³ each, independently of one another and on each        occurrence identically or differently, denote

-   -   Z²¹, Z²² each, independently of one another and on each        occurrence identically or differently, denote a single bond,        —(CH₂)₄—, —CH₂CH₂—, —CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CH═CH—,        —CF═CF—, —CF═CH—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—, —C≡C—, —CH₂O—,        —OCH₂—, —CF₂O—, —OCF₂—, —CO—O— or —O—CO—,    -   X²² denotes F, Cl, —CN, —NCS, —SF₅, —SO₂CF₃, or alkyl, alkenyl,        alkenyloxy, alkylalkoxy or alkoxy having 1 to 3 C atoms, which        is mono- or polysubstituted by F, Cl or CN,    -   L²¹, L²² each, independently of one another, denote H or F,    -   m denotes 0, 1 or 2,    -   n denotes 0, 1, 2 or 3,    -   o denotes 0, 1 or 2, where    -   m+n+o denotes 0, 1, 2 or 3, preferably 0, 1 or 2,    -   optionally a liquid-crystalline component C comprising one or        more, preferably two or more, low-molecular-weight (i.e.        monomeric and unpolymerisable) compounds, preferably in a        concentration of 1 to 25%, preferably consisting principally of,        very particularly preferably consisting exclusively of, one or        more compounds of the formula III

-   -   in which    -   a, b, c, d each, independently of one another, denote 0, 1 or 2,        where    -   a+b+c+d is 0, 1, 2, 3 or 4,    -   A³¹, A³², A³³, A³⁴ each, independently of one another and on        each occurrence identically or differently, denote

-   -   Z³¹, Z³², Z³³, Z³⁴ each, independently of one another and on        each occurrence identically or differently, denote a single        bond, —(CH₂)₄)—, —CH₂CH₂—, —CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—,        —CH═CH—, —CF═CF—, —CF═CH—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—, —C≡C—,        —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CO—O— or —O—CO—,    -   R³³ denotes alkyl or alkoxy having 1 to 15 C atoms, which is        unsubstituted or mono- or polysubstituted by F, Cl or CN, and in        which, in addition, one or more non-adjacent CH₂ groups may also        each be replaced, independently of one another, by —O—, —S—,        —SiR^(x)R^(y)—, —CH═CH—, —C≡C—, —CO—O— and/or —O—CO— in such a        way that O and/or S atoms are not linked directly to one        another, preferably a straight-chain alkyl, alkoxy, alkenyl,        alkenyloxy or —O-alkylene-O— radical having up to 10 C atoms,        which is unsubstituted or mono- or polysubstituted by F or Cl,    -   L³¹, L³², L³³, L³⁴ each, independently of one another, denote H,        F, Cl, CN, or alkyl or alkoxy having 1 to 15 C atoms, which is        unsubstituted or mono- or polysubstituted by F, Cl or CN, and in        which, in addition, one or more non-adjacent CH₂ groups may also        each be replaced, independently of one another, by —O—, —S—,        —SiR^(x)R^(y)—, —CH═CH—, —C≡C—, —CO—O— and/or —O—CO— in such a        way that O and/or S atoms are not linked directly to one        another, with the proviso that at least one of the radicals L³¹,        L³², L³³, and L³⁴ is other than H,    -   X³³ denotes F, Cl, CF₃, OCF₃, CN, NCS, —SF₅ or —SO₂—R^(z),    -   R^(x) and R^(y) each, independently of one another, denote H,        alkyl or alkoxy having 1 to 7 C atoms, preferably methyl, ethyl,        propyl or butyl, and    -   R^(z) denotes alkyl having 1 to 7 C atoms, which is        unsubstituted or mono- or polysubstituted by F or Cl, preferably        CF₃, C₂F₅ or n-C₄F₉,    -   a component D, preferably in a concentration of 1-20%,        comprising one or more optically active and/or chiral compounds,        preferably having an HTP≧20 μm, preferably ≧40 μm, very        particularly preferably ≧60 μm.

The chiral component D preferably comprises one or more chiral compoundshaving a mesogenic structure and preferably has one or more mesophases,particularly preferably at least cholesteric phase. Preferred chiralcompounds of component D are, for example, chiral dopants which areknown from the prior art and/or are commercially available, such ascholesteryl nonanoate (CN), R/S-811, R/S-1011, R/S-2011, R/S-3011,R/S-4011, R/S-5011 or CB-15 (Merck KGaA, Darmstadt). Particularpreference is given to chiral dopants containing one or more chiralgroups and one or more mesogenic groups, as disclosed, for example, inDE 34 25 503, DE 35 34 777, DE 35 34 778, DE 35 34 779, DE 35 34 780, DE43 42 280, EP 01 038 941 and DE 195 41 820. Preference is furthermoregiven to sorbitols, as described, for example, in WO 98/00428 A1,hydrobenzoins, as described, for example, in GB 2 328 207 A, chiralbinaphthols, as described, for example, WO 02/94805 A1, chiralbinaphthol acetals, as described, for example, in WO 02/34739 A1, chiralTADDOLs, as described, for example, in WO 02/06265 A1, or chiralcompounds containing fluorinated bridging groups, as described, forexample, in WO 02/06196 A1 or WO 02/06195 A1.

The clearing point of the LC medium according to the invention having ablue phase is preferably in the range from −30° C. to 100° C.

The LC medium preferably comprises one, two, three, four or more thanfour chiral compounds. The LC medium preferably comprises chiralcompounds in a total concentration of 0.01 to 25%, preferably 0.1-20%,particularly preferably 0.5 to 20%, very particularly 3-15%.

The proportion of the compounds of the formula I in the total content ofall polymerisable compounds in the LC medium, or the proportion of thecompounds of the formula I in the polymerisable component A), ispreferably 20 to 80%, particularly preferably 40 to 60%.

In a further preferred embodiment, the proportion of the compounds ofthe formula I in the total content of all polymerisable compounds in theLC medium, or the proportion of the compounds of the formula I in thepolymerisable component A), is at least 50% and particularly preferably60% to 100%.

Further particularly preferred embodiments are described below:

-   -   The LC medium comprises one, two or three compounds of the        formula I;    -   C omponent B comprises, in addition to the compounds of the        formula II, one or more ester compounds of the formula Z:

-   -   in which R^(z) has one of the meanings indicated for R²² in        formula II,

-   -    denotes

-   -   X^(Z) denotes F, Cl, CN, NCS, OCF₃, CF₃ or SF₅, and (F) denotes        F or H,    -   preferably in a concentration of 5 to 35%, particularly        preferably 10 to 30%, very particularly preferably 10 to 20%.    -   Component B comprises, in addition to the compounds of the        formula II, one or more compounds of the formula N:

-   -   in which R^(N) has one of the meanings indicated for R²² in        formula II and preferably denotes alkyl or alkyl-C≡C, “alkyl”        denotes alkyl having 1 to 7 C atoms, which is preferably        straight-chain, (F) denotes F or H, and n denotes 0 or 1.    -   Component B comprises, in addition to the compounds of the        formula II, one or more compounds of the formula E:

-   -   in which R^(E) has one of the meanings indicated for R²² in        formula II and preferably denotes C1-C7-alkyl, and

-   -    denotes

-   -   preferably in a concentration of 10-30%, particularly preferably        15-25%.    -   The LC medium additionally comprises one or more compounds of        the formulae Q1 and/or Q2:

-   -   in which R^(Q) has one of the meanings indicated for R²² in        formula II, X^(Q) has one of the meanings indicated for X^(E) in        formula E, and n and m each, independently of one another,        denote 0 or 1.    -   The LC medium additionally comprises one or more compounds of        the formulae Dx1 and/or Dx2:

-   -   in which R^(D) has one of the meanings indicated for R²² in        formula II.

Particular preference is given to LC media which, besides one or morecompounds of the formula I, comprise one or more compounds of theformula II, in particular in which X²² denotes F, Cl, CN, NCS, CF₃ orOCF₃.

The compounds of the formulae I, II, III, Z, N, E, Q1, Q2, Dx1 and Dx2are colourless, stable and readily miscible with one another or withother liquid-crystalline substances.

The individual components and compounds of the formulae I, II, III, Z,N, E, Q1, Q2, Dx1 and Dx2 of the LC media according to the invention areeither known or methods for the preparation thereof can readily bederived from the prior art by the person skilled in the relevant art,since they are based on standard methods described in the literature.

The LC media according to the invention are prepared in a mannerconventional per se, for example by mixing one or more of theabove-mentioned compounds with one or more polymerisable compounds asdefined above, and optionally with further liquid-crystalline compoundsand/or additives. In general, the desired amount of the components usedin lesser amount is dissolved in the components making up the principalconstituent, advantageously at elevated temperature. It is also possibleto mix solutions of the components in an organic solvent, for example inacetone, chloroform or methanol, and to remove the solvent again, forexample by distillation, after thorough mixing. The inventionfurthermore relates to the process for the preparation of the LC mediaaccording to the invention.

The LC media according to the invention for LC displays having a bluephase may also comprise further additives known to the person skilled inthe art and described in the literature, such as, for example,polymerisation initiators, inhibitors, stabilisers or surface-activesubstances. These may be polymerisable or unpolymerisable. Polymerisableadditives are accordingly ascribed to the polymerisable component.Unpolymerisable additives are accordingly ascribed to theliquid-crystalline component.

The structure of the LC displays according to the invention having ablue phase, with polarisers, electrode substrates and surface-treatedelectrode layers, corresponds to the conventional structure for displaysof this type which is known to the person skilled in the art, asdescribed in the prior art, for example in DE 102 17 273 A1, DE 102 41301, DE 102 17 273 A1, DE 102 41 301, DE 102 536 06, DE 103 13 979.

An LC display according to the invention preferably comprises thefollowing components

-   -   one or two substrates,    -   an electrode arrangement having two electrodes on only one of        the two substrates or having one electrode on each of the two        substrates, one or two polarisers, and    -   a layer of an LC medium according to the invention located        between the two substrates,        where the display is operated at a temperature at which the LC        medium in the unswitched state has an optically isotropic phase,        preferably a blue phase.

The phase transition of the LC medium into the blue phase usually takesplace starting from a cholesteric phase which exists at lowertemperatures than the blue phase. The operating temperature of the LCdisplay according to the invention (i.e. after polymer stabilisation) ispreferably above the temperature of the phase transition of the LCmedium into the blue phase (i.e. usually the cholesteric phase-bluephase transition), particularly preferably from 0.1 to 50°, veryparticularly preferably from 0, to 40°, above this phase-transitiontemperature. Furthermore, the operating temperature of the LC display ispreferably below the temperature of the phase transition of the LCmedium from the blue phase into the isotropic phase (also known as theclearing point). However, the display can also be operated in theisotropic phase, i.e. above the clearing point.

The LC media according to the invention having a blue phase may, inaddition to the above-mentioned compounds of the formulae II and III,and in addition or alternatively to the above-mentioned compounds of theformulae Z, N, E, Q1, Q2, Dx1 and Dx2, also comprise furtherliquid-crystalline compounds in order, for example, to adapt thephysical properties. Such compounds are known to the person skilled inthe art. Their concentration in the LC media is preferably 0 to 30%,particularly preferably 0 to 20%, very particularly preferably 5 to 15%.

The liquid-crystalline component of an LC medium according to theinvention (i.e. before polymer stabilisation) preferably has atemperature range of the blue phase, or, if a plurality of sequentialblue phases occur, a combined temperature range of all blue phases,whose total width is 2° C. or more, preferably 5° C. or more,particularly preferably 10° C. or more, very particularly preferably 20°C. or more.

The liquid-crystalline component of an LC medium according to theinvention (i.e. before polymer stabilisation) preferably exhibits atemperature range of the blue phase(s) at least in the range from 10° C.to 30° C., particularly preferably from 10° C. to 40° C., veryparticularly preferably from 0° C. to 50° C.

“At least” above and below means that the blue phase(s) may also extendbelow the lower limit value indicated in each case and/or above theupper limit value indicated in each case.

In a further preferred embodiment, the liquid-crystalline component ofan LC medium according to the invention (i.e. before polymerstabilisation) exhibits a temperature range of the blue phase(s) atleast in the range from 20° C. to 40° C., particularly preferably atleast from 30° C. to 80° C., very particularly preferably at least from30° C. to 90° C. Preference is furthermore given to LC media having atemperature range of the blue phase(s) at least from −20° C. to 50° C.

An LC medium according to the invention comprising the polymerisedcomponent (i.e. after polymer stabilisation) preferably exhibits atemperature range of the blue phase(s) at least in the range from 30° C.to 70° C., preferably from 20° C. to 70° C., particularly preferablyfrom 0° C. to 80° C., very particularly preferably from −20° C. to 80°C.

The phase-transition temperatures of an LC medium according to theinvention comprising the polymerisable component, in particular theclearing point and/or the temperature of the transition from thecholesteric phase into the blue phase (T(Ch,BP), also known as T(N*,BP),and/or the temperature of the transition from the blue phase into theisotropic phase (T(BP,I)), are preferably not reduced by thepolymerisation of the polymerisable component. This means that thepolymer stabilisation the blue phase(s) is preferably carried out insuch a way that one or more of the phase-transition temperatures(T(Ch,BP), T(BP,I)) indicated above are not shifted to lowertemperatures, i.e. the blue phase(s) is (are) preferably broadened atleast to lower temperatures and particularly preferably both to lowerand to higher temperatures.

Particularly preferred LC media for use in PSA displays, in particularin PSA-VA, PSA-OCB, PSA-IPS, PSA-FFS or PSA-TN displays, are describedbelow.

An LC medium according to the invention for use in PSA-VA, PSA-OCB,PSA-IPS, PSA-FFS or PSA-TN displays according to the inventionpreferably comprises:

-   -   <5%, particularly preferably <1%, very particularly preferably        <0.5%, of the polymerisable component,    -   >95%, particularly preferably >99%, of the liquid-crystalline        component,    -   <5% by weight, particularly preferably <1% by weight, very        particularly preferably <0.5% by weight, of polymerisable        compounds, in particular polymerisable compounds of the formulae        I mentioned above or sub-formulae thereof,    -   one, two or three polymerisable compounds of the formula I or        sub-formulae thereof according to the invention,    -   a polymerisable component which comprises exclusively        polymerisable compounds of the formula I or sub-formulae thereof        according to the invention,    -   a liquid-crystalline component which is an LC compound or an LC        mixture which has a nematic liquid-crystal phase,    -   a polymerisable and/or liquid-crystalline component which        comprises exclusively achiral compounds,    -   a polymerisable component which comprises one or more        polymerisable compounds containing one polymerisable group        (monoreactive) and one or more polymerisable compounds according        to the invention containing two or more, preferably two,        polymerisable groups (di- or multireactive), preferably selected        from compounds of the formula I or sub-formulae thereof, and        optionally from the above-mentioned comonomers selected from the        list comprising the formulae M1-M29,    -   a polymerisable component which comprises exclusively        polymerisable compounds according to the invention containing        two polymerisable groups (direactive), preferably selected from        compounds of the formula I or sub-formulae thereof, and        optionally additionally from the above-mentioned comonomers from        the list comprising the formulae M1-M29,    -   apart from the polymerisable compounds according to the        invention, in particular of the formula I or sub-formulae        thereof, and the comonomers, no compounds which contain a        terminal vinyloxy group (—O—CH═CH₂),    -   1 to 5, preferably 1, 2 or 3, polymerisable compounds,        preferably selected from polymerisable compounds according to        the invention, in particular of the formula I or sub-formulae        thereof.

Particularly preferred LC media for use in PSA-VA displays are indicatedbelow:

-   a) LC medium which comprises one or more compounds of the formulae    CY and/or PY:

-   -   in which the individual radicals have the following meanings:    -   a denotes 1 or 2,    -   b denotes 0 or 1,

-   -    denotes

-   -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another, preferably alkyl or alkoxy having 1 to        6 C atoms,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,        —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond,    -   L¹-4 each, independently of one another, denote F, Cl, OCF₃,        CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl, or both        radicals L³ and L⁴ denote F or one of the radicals L³ and L⁴        denotes F and the other denotes Cl.    -   The compounds of the formula CY are preferably selected from the        group consisting of the following sub-formulae

-   -   in which a denotes 1 or 2, alkyl and alkyl* each, independently        of one another, denote a straight-chain alkyl radical having 1-6        C atoms, and alkenyl denotes a straight-chain alkenyl radical        having 2-6 C atoms, and (O) denotes an oxygen atom or a single        bond. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)₂—.    -   The compounds of the formula PY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl        preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.

-   b) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals have the following meaning

-   -    denotes

-   -    denotes

-   -   R³ and R⁴ each, independently of one another, denote alkyl        having 1 to 12 C atoms, in which, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —O—CO— or —CO—O— in such a way that O atoms are not linked        directly to one another,    -   Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond.    -   The compounds of the formula ZK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—,        CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH—        or CH₃—CH═CH—(CH₂)₂—.

-   c) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals on each occurrence, identically        or differently, have the following meanings:    -   R⁵ and R⁶ each, independently of one another, have one of the        meanings indicated above for R¹,

-   -    denotes

-   -    denotes

-   -    and    -   e denotes 1 or 2.    -   The compounds of the formula DK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.

-   d) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals have the following meaning

-   -    denotes

-   -   f denotes 0 or 1,    -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —OCO— or —COO— in such a way that O atoms are not linked        directly to one another,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,        —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond,    -   L¹ and L² each, independently of one another, denote F, Cl,        OCF₃, CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl.    -   The compounds of the formula LY are preferably selected from the        group consisting of the following sub-formulae

-   -   in which R¹ has the meaning indicated above, alkyl denotes a        straight-chain alkyl radical having 1-6 C atoms, (O) denotes an        oxygen atom or a single bond, and v denotes an integer from 1        to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C        atoms or straight-chain alkenyl having 2 to 6 C atoms, in        particular CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂═CH—,        CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—,        CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   e) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which alkyl denotes C₁₋₆-alkyl, L^(x) denotes H or F, and X        denotes F, Cl, OCF₃, OCHF₂ or OCH═CF₂. Particular preference is        given to compounds of the formula G1 in which X denotes F.

-   f) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁵ has one of the meanings indicated above for R¹,        alkyl denotes C₁₋₆-alkyl, d denotes 0 or 1, and z and m each,        independently of one another, denote an integer from 1 to 6. R⁵        in these compounds is particularly preferably C₁₋₆-alkyl or        -alkoxy or C₂₋₆-alkenyl, d is preferably 1. The LC medium        according to the invention preferably comprises one or more        compounds of the above-mentioned formulae in amounts of 5% by        weight.

-   g) LC medium which additionally comprises one or more biphenyl    compounds selected from the group consisting of the following    formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The proportion of the biphenyls of the formulae B1 to B3 in the        LC mixture is preferably at least 3% by weight, in particular 5%        by weight.    -   The compounds of the formula B2 are particularly preferred.    -   The compounds of the formulae B1 to B3 are preferably selected        from the group consisting of the following sub-formulae:

-   -   in which alkyl* denotes an alkyl radical having 1-6 C atoms. The        medium according to the invention particularly preferably        comprises one or more compounds of the formulae B1a and/or B2c.

-   h) LC medium which additionally comprises one or more terphenyl    compounds of the following formula:

-   -   in which R⁵ and R⁶ each, independently of one another, have one        of the meanings indicated above for R¹, and

-   -   each, independently of one another, denote

-   -   in which L⁵ denotes F or Cl, preferably F, and L⁶ denotes F, Cl,        OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F.    -   The compounds of the formula T are preferably selected from the        group consisting of the following sub-formulae

-   -   in which R denotes a straight-chain alkyl or alkoxy radical        having 1-7 C atoms, R* denotes a straight-chain alkenyl radical        having 2-7 C atoms, (O) denotes an oxygen atom or a single bond,        and m denotes an integer from 1 to 6. R* preferably denotes        CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,        CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.    -   R preferably denotes methyl, ethyl, propyl, butyl, pentyl,        hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.    -   The LC medium according to the invention preferably comprises        the terphenyls of the formula T and the preferred sub-formulae        thereof in an amount of 0.5-30% by weight, in particular 1-20%        by weight.    -   Particular preference is given to compounds of the formulae T1,        T2, T3 and T21. In these compounds, R preferably denotes alkyl,        furthermore alkoxy, each having 1-5 C atoms.    -   The terphenyls are preferably employed in mixtures according to        the invention if the Δn value of the mixture is to be ≧0.1.        Preferred mixtures comprise 2-20% by weight of one or more        terphenyl compounds of the formula T, preferably selected from        the group of compounds T1 to T22.

-   i) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R¹ and R² have the meanings indicated above and        preferably each, independently of one another, denote        straight-chain alkyl having 1 to 6 C atoms or straight-chain        alkenyl having 2 to 6 C atoms.    -   Preferred media comprise one or more compounds selected from the        formulae O1, O3 and O4.

-   k) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which

-   -    denotes

-   -   R⁹ denotes H, CH₃, C₂H₅ or n-C₃H₇, (F) denotes an optional        fluorine substituent, and q denotes 1, 2 or 3, and R⁷ has one of        the meanings indicated for R¹, preferably in amounts of >3% by        weight, in particular ≧5% by weight and very particularly        preferably 5-30% by weight.    -   Particularly preferred compounds of the formula F1 are selected        from the group consisting of the following sub-formulae:

-   -   in which R⁷ preferably denotes straight-chain alkyl, and R⁹        denotes CH₃, C₂H₅ or n-C₃H₇. Particular preference is given to        the compounds of the formulae FI1, FI2 and FI3.

-   m) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁸ has the meaning indicated for R¹, and alkyl denotes        a straight-chain alkyl radical having 1-6 C atoms.

-   n) LC medium which additionally comprises one or more compounds    which contain a tetrahydronaphthyl or naphthyl unit, such as, for    example, the compounds selected from the group consisting of the    following formulae:

-   -   in which R¹⁰ and R¹¹ each, independently of one another, have        one of the meanings indicated for R¹, preferably denote        straight-chain alkyl or alkoxy having 1 to 6 C atoms or        straight-chain alkenyl having 2 to 6 C atoms, and Z¹ and Z²        each, independently of one another, denote —C₂H₄—, —CH═CH—,        —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CH—CH₂CH₂—, —CH₂CH₂CH═CH—,        —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CF═CH—,        —CH═CF—, —CH₂— or a single bond.

-   o) LC medium which additionally comprises one or more    difluoro-dibenzochromans and/or chromans of the following formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        the meaning indicated above, and c denotes 0 or 1, preferably in        amounts of 3 to 20% by weight, in particular in amounts of 3 to        15% by weight.    -   Particularly preferred compounds of the formulae BC and CR are        selected from the group consisting of the following        sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   Very particular preference is given to mixtures comprising one,        two or three compounds of the formula BC-2.

-   p) LC medium which additionally comprises one or more fluorinated    phenanthrenes and/or dibenzofurans of the following formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        the meanings indicated above, b denotes 0 or 1, L denotes F, and        r denotes 1, 2 or 3.    -   Particularly preferred compounds of the formulae PH and BF are        selected from the group consisting of the following        sub-formulae:

-   -   in which R and R′ each, independently of one another, denote a        straight-chain alkyl or alkoxy radical having 1-7 C atoms.

-   q) LC medium which comprises 1 to 8, preferably 1 to 5, compounds of    the formulae CY1, CY2, PY1 and/or PY2. The proportion of these    compounds in the mixture as a whole is preferably 5 to 60%,    particularly preferably 10 to 35%. The content of these individual    compounds is preferably in each case 2 to 20%.

-   r) LC medium which comprises 1 to 8, preferably 1 to 5, compounds of    the formulae CY9, CY10, PY9 and/or PY10. The proportion of these    compounds in the mixture as a whole is preferably 5 to 60%,    particularly preferably 10 to 35%. The content of these individual    compounds is preferably in each case 2 to 20%.

-   s) LC medium which comprises 1 to 10, preferably 1 to 8, compounds    of the formula ZK, in particular compounds of the formulae ZK1, ZK2    and/or ZK6. The proportion of these compounds in the mixture as a    whole is preferably 3 to 25%, particularly preferably 5 to 45%. The    content of these individual compounds is preferably in each case 2    to 20%.

-   t) LC medium in which the proportion of compounds of the formulae    CY, PY and ZK in the mixture as a whole is greater than 70%,    preferably greater than 80%.

-   u) PSA-VA display in which the pretilt angle is preferably 86°.

Particularly preferred LC media for use in PSA-OCB, PSA-TN, PSA-IPS orPSA-FFS displays are indicated below:

-   a) LC medium which comprises one or more compounds selected from the    group consisting of the following formulae:

-   -   in which    -   R⁰ on each occurrence, identically or differently, denotes        n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having        up to 9 C atoms,    -   X⁰ denotes F, Cl or in each case halogenated alkyl, alkenyl,        alkenyloxy or alkoxy, each having up to 6 C atoms,    -   Z⁰ denotes —CF₂O— or a single bond,    -   Y¹⁻⁶ each, independently of one another, denote H or F.    -   X⁰ is preferably F, Cl, CF₃, CHF₂, OCF₃, OCHF₂, OCFHCF₃,        OCFHCHF₂, OCFHCHF₂, OCF₂CH₃, OCF₂CHF₂, OCF₂CHF₂, OCF₂CF₂CHF₂,        OCF₂CF₂CHF₂, OCFHCF₂CF₃, OCFHCF₂CHF₂, OCF₂CF₂CF₃, OCF₂CF₂CClF₂,        OCClFCF₂CF₃ or CH═CF₂, particularly preferably F or OCF₃.    -   The compounds of the formula AA are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above, and X⁰        preferably denotes F. Particular preference is given to        compounds of the formulae AA2 and AA6.    -   The compounds of the formula BB are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above, and X⁰        preferably denotes F. Particular preference is given to        compounds of the formulae BB1, BB2 and BBS.    -   The compounds of the formula CC are preferably selected from the        following formula:

-   -   in which R⁰ on each occurrence, identically or differently, has        the meaning indicated above and preferably denotes alkyl having        1 to 6 C atoms.

The combination of compounds of the preferred embodiments a)-y)mentioned above with the polymerised compounds described above causeslow threshold voltages, low rotational viscosities and very goodlow-temperature stabilities in the LC media according to the inventionat the same time as constantly high clearing points and high HR values,and allows the rapid establishment of a particularly low pretilt anglein PSA displays. In particular, the LC media exhibit significantlyshortened response times, in particular also the grey-shade responsetimes, in PSA displays compared with the media from the prior art.

The liquid-crystal mixture preferably has a nematic phase range of atleast 80 K, particularly preferably at least 100 K, and a rotationalviscosity of not greater than 250 mPa·s, preferably not greater than 200mPa·s, at 20° C.

LC media according to the invention for use in displays of the PSA-VAtype have negative dielectric anisotropy Δ∈, preferably from about −0.5to −10, in particular from about −2.5 to −7.5 at 20° C. and 1 kHz.

In VA-type displays according to the invention, the molecules in thelayer of the LC medium in the switched-off state are alignedperpendicular to the electrode surfaces (homeotropically) or have atilted homeotropic alignment. On application of an electrical voltage tothe electrodes, a re-alignment of the LC molecules takes place with thelongitudinal molecular axes parallel to the electrode surfaces.

In OCB-type displays according to the invention, the molecules in thelayer of the LC medium are on a “bend” alignment. On application of anelectrical voltage, re-alignment of the LC molecules takes place withthe longitudinal molecular axes perpendicular to the electrode surfaces.

LC media according to the invention for use in displays of the PSA-OCBtype preferably have positive dielectric anisotropy Δ∈, preferably fromabout +4 to +17 at 20° C. and 1 kHz.

The birefringence Δn in LC media according to the invention for use indisplays of the VA type is preferably less than 0.16, particularlypreferably between 0.06 and 0.14, in particular between 0.07 and 0.12.

The birefringence Δn in LC media according to the invention for use indisplays of the OCB type is preferably between 0.14 and 0.22, inparticular between 0.16 and 0.22.

The birefringence Δn in LC media according to the invention for use indisplays of the PSA-TN, PSA-IPS or PSA-FFS type is preferably between0.07 and 0.15, in particular between 0.08 and 0.13. The dielectricanisotropy of these media is preferably between +2 and +17, inparticular between +3 and +15.

The LC media according to the invention may also comprise furtheradditives known to the person skilled in the art and described in theliterature, such as, for example, polymerisation initiators, inhibitors,stabilisers, surface-active substances or chiral dopants. These may bepolymerisable or unpolymerisable. Polymerisable additives areaccordingly ascribed to the polymerisable component. Unpolymerisableadditives are accordingly ascribed to the liquid-crystalline component.

The LC media may, for example, comprise one or more chiral dopants,preferably those selected from the group consisting of compounds fromTable B below.

Furthermore, it is possible to add to the LC media, for example, 0 to15% by weight of pleochroic dyes, furthermore nanoparticles, conductivesalts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate,tetrabutylammonium tetraphenylborate or complex salts of crown ethers(cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258(1973)), for improving the conductivity, or substances for modifying thedielectric anisotropy, the viscosity and/or the alignment of the nematicphases. Substances of this type are described, for example, in DE-A 2209 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53728.

The individual components of the preferred embodiments a)-z) of the LCmedia according to the invention are either known or methods for thepreparation thereof can readily be derived from the prior art by theperson skilled in the relevant art, since they are based on standardmethods described in the literature. Corresponding compounds of theformula CY are described, for example, in EP-A-0 364 538. Correspondingcompounds of the formula ZK are described, for example, in DE-A-26 36684 and DE-A-33 21 373.

The LC media which can be used in accordance with the invention areprepared in a manner conventional per se, for example by mixing one ormore of the above-mentioned compounds with one or more polymerisablecompounds as defined above, and optionally with furtherliquid-crystalline compounds and/or additives. In general, the desiredamount of the components used in lesser amount is dissolved in thecomponents making up the principal constituent, advantageously atelevated temperature. It is also possible to mix solutions of thecomponents in an organic solvent, for example in acetone, chloroform ormethanol, and to remove the solvent again, for example by distillation,after thorough mixing. The invention furthermore relates to the processfor the preparation of the LC media according to the invention.

It goes without saying to the person skilled in the art that the LCmedia according to the invention may also comprise compounds in which,for example, H, N, O, Cl, F have been replaced by the correspondingisotopes.

The structure of the PSA displays according to the invention correspondsto the usual geometry for PSA displays, as described in the prior artcited at the outset. Geometries without protrusions are preferred, inparticular those in which, in addition, the electrode on the colourfilter side is unstructured and only the electrode on the TFT side hasslots. Particularly suitable and preferred electrode structures forPSA-VA displays are described, for example, in US 2006/0066793 A1.

The following examples explain the present invention without restrictingit. However, they show the person skilled in the art preferred mixtureconcepts with compounds preferably to be employed and the respectiveconcentrations thereof and combinations thereof with one another. Inaddition, the examples illustrate which properties and propertycombinations are accessible.

The following abbreviations are used:

(m, m, z: in each case, independently of one another, 1, 2, 3, 4, 5 or6)

TABLE A

In a preferred embodiment of the present invention, the LC mediaaccording to the invention comprise one or more compounds selected fromthe group consisting of compounds from Table A.

TABLE B Table B shows possible chiral dopants which can be added to theLC media according to the invention.

The LC media preferably comprise 0 to 10% by weight, in particular 0.01to 5% by weight, particularly preferably 0.1 to 3% by weight, ofdopants. The LC media preferably comprise one or more dopants selectedfrom the group consisting of compounds from Table B.

TABLE C Table C shows possible stabilisers which can be added to the LCmedia according to the invention. (n here denotes an integer from 1 to12, preferably 1, 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups are notshown).

The LC media preferably comprise 0 to 10% by weight, in particular 1 ppmto 5% by weight, particularly preferably 1 ppm to 1% by weight, ofstabilisers. The LC media preferably comprise one or more stabilisersselected from the group consisting of compounds from Table C.

TABLE D Table E shows illustrative compounds which can be used in the LCmedia in accordance with the present invention, preferably as reactivemesogenic compounds.

RM-1

RM-2

RM-3

RM-4

RM-5

RM-6

RM-7

RM-8

RM-9

RM-10

RM-11

RM-12

RM-13

RM-14

RM-15

RM-16

RM-17

RM-18

RM-19

RM-20

RM-21

RM-22

RM-23

RM-24

RM-25

RM-26

RM-27

RM-28

In a preferred embodiment of the present invention, the mesogenic mediacomprise one or more compounds selected from the group of the compoundsfrom Table D.

In addition, the following abbreviations and symbols are used:

-   V₀ threshold voltage, capacitive [V] at 20° C.,-   n_(e) extraordinary refractive index at 20° C. and 589 nm,-   n_(o) ordinary refractive index at 20° C. and 589 nm,-   Δn optical anisotropy at 20° C. and 589 nm,-   ∈_(⊥) dielectric permittivity perpendicular to the director at    20° C. and 1 kHz,-   ∈_(∥) dielectric permittivity parallel to the director at 20° C. and    1 kHz,-   Δ∈ dielectric anisotropy at 20° C. and 1 kHz,-   cl.p., T(N,I) clearing point [° C.],-   γ₁ rotational viscosity at 20° C. [mPa·s],-   K₁ elastic constant, “splay” deformation at 20° C. [pN],-   K₂ elastic constant, “twist” deformation at 20° C. [pN],-   K₃ elastic constant, “bend” deformation at 20° C. [pN].

Unless explicitly noted otherwise, all concentrations in the presentapplication are quoted in percent by weight and relate to thecorresponding mixture as a whole, comprising all solid orliquid-crystalline components, without solvents.

Unless explicitly noted otherwise, all temperature values indicated inthe present application, such as, for example, for the melting pointT(C,N), the transition from the smectic (S) to the nematic (N) phaseT(S,N) and the clearing point T(N,I), are quoted in degrees Celsius (°C.). M.p. denotes melting point, cl.p.=clearing point. Furthermore,C=crystalline state, N=nematic phase, S=smectic phase and I=isotropicphase. The data between these symbols represent the transitiontemperatures.

All physical properties are and have been determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, StatusNovember 1997, Merck KGaA, Germany, and apply for a temperature of 20°C., and Δn is determined at 589 nm and Δ∈ at 1 kHz, unless explicitlyindicated otherwise in each case.

The term “threshold voltage” for the present invention relates to thecapacitive threshold (V₀), also known as the Freedericks threshold,unless explicitly indicated otherwise. In the examples, the opticalthreshold may also, as generally usual, be quoted for 10% relativecontrast (V₁₀).

The display used for measurement of the capacitive threshold voltageconsists of two plane-parallel glass outer plates at a separation of 20μm, each of which has on the inside an electrode layer and an unrubbedpolyimide alignment layer on top, which effect a homeotropic edgealignment of the liquid-crystal molecules.

The display or test cell used for measurement of the tilt anglesconsists of two plane-parallel glass outer plates at a separation of 4μm, each of which has on the inside an electrode layer and a polyimidealignment layer on top, where the two polyimide layers are rubbedantiparallel to one another and effect a homeotropic edge alignment ofthe liquid-crystal molecules.

The polymerisable compounds are polymerised in the display or test cellby irradiation with UVA light (usually 365 nm) of defined intensity fora pre-specified time, with a voltage simultaneously being applied to thedisplay (usually 10 V to 30 V alternating current, 1 kHz). In theexamples, unless indicated otherwise, a 50 mW/cm² mercury vapour lamp isused, and the intensity is measured using a standard UV meter (modelUshio UNI meter) fitted with a 365 nm band-pass filter.

The tilt angle is determined by a crystal rotation experiment(Autronic-Melchers TBA-105). A low value (i.e. a large deviation fromthe 90° angle) corresponds to a large tilt here.

The VHR value is measured as follows: 0.3% of a polymerisable monomericcompound is added to the LC host mixture, and the resultant mixture isintroduced into TN-VHR test cells (rubbed at 90°, TN-polyimide alignmentlayer, layer thickness d≈6 μm). The HR value is determined after 5 minat 100° C. before and after UV exposure for 2 h (sun test) at 1 V, 60Hz, 64 μs pulse (measuring instrument: Autronic-Melchers VHRM-105).

In order to investigate the low-temperature stability, also referred toas “LTS”, i.e. the stability of the LC mixture to individual componentsspontaneously crystallising out at low temperatures, bottles containing1 g of LC/RM mixture are placed in storage at −10° C., and it isregularly checked whether the mixtures have crystallised out.

The so-called “HTP” (“helical twisting power”) denotes the helicaltwisting power of an optically active or chiral substance in an LCmedium (in μm). Unless indicated otherwise, the HTP is measured in thecommercially available nematic LC host mixture MLD-6260 (Merck KGaA) ata temperature of 20° C.

EXAMPLE 16-(4-{2-[3-Methyl-4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}phenyl)hexyl2-methacrylate (1)

Compound (1) according to the invention,6-(4-{2-[3-methyl-4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}phenyl)hexyl2-methacrylate (1), is synthesised as described below.

1.1 Preparation of 1,4-bis[2-(4-bromophenyl)vinyl]-2-methylbenzene (E/ZMixture)

6.30 g (42.5 mmol) of 2-methylbenzenedicarbaldehyde are initiallyintroduced in 150 ml of dichloromethane together with 50.0 g (97.6 mmol)of 4-bromobenyzltriphenylphosphonium bromide and 2.50 g (9.47 mmol) of18-crown-6. 11.0 g (0.20 mol) of powdered KOH are added in portions at−70° C. The mixture is stirred at −70° C. for 2 h, and the batch iswarmed to room temperature. After 1 h at this temperature, water isadded, and the organic phase is separated off.

The aqueous phase is extracted with dichloromethane, and the combinedorganic phases are washed with sat. ammonium chloride soln. The solutionis filtered absorptively (SiO₂, CH₂Cl₂), and the filtrate isconcentrated to dryness. The crude product is purified by columnchromatography (SiO₂, toluene:n-heptane=1:1).E/Z-1,4-bis-[2-(4-bromophenyl)vinyl]-2-methylbenzene is obtained as ayellow oil.

1.2 Preparation of6-{4-[(2-(4-{2-[4-(6-hydroxyhex-1-ynyl)phenyl]vinyl}-3-methylphenyl)vinyl]phenyl}hex-5-yn-1-ol(E/Z Mixture)

A mixture of 18.0 g (39.6 mmol) ofE/Z-1,4-bis-[2-(4-bromophenyl)vinyl]-2-methylbenzene, 2.78 g (3.96 mmol)of bis(triphenylphosphine)palladium-(II) chloride, 755 mg (3.96 mmol) ofcopper(I) iodide and 28.0 ml (0.20 mol) of triethylamine in 150 ml ofDMF is warmed to 60° C. 15.3 ml of 5-hexyn-1-ol dissolved in 50 ml ofDMF are metered in. When the addition is complete, the batch is stirredat 75° C. for 18 h. After cooling, the mixture is diluted with THF/MTBEand neutralised using dil. hydrochloric acid. The organic phase isseparated off, and the aqueous phase is extracted with MTBE. Thecombined organic phase is washed with sodium chloride solution and driedusing sodium sulfate. The solution is concentrated to dryness, and theresidue is purified by column chromatography (SiO₂, toluene:ethylacetate=1:1).

1.3 Preparation of6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}-2-methylphenyl)ethyl]phenyl}hexan-1-ol

9.5 g (19.4 mmol) of6-{4-[(2-(4-{2-[4-(6-hydroxyhex-1-ynyl)phenyl]vinyl}-3-methylphenyl)vinyl]phenyl}hex-5-yn-1-ol(E/Z mixture) are hydrogenated at room temperature for 19 h in thepresence of Pd/C (5% of Pd) in THF. The solution is filtered andconcentrated to dryness. The residue is recrystallised fromn-heptane/MTBE (1:1), giving6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}-2-methylphenylethyl]phenyl}hexan-1-olas a colourless solid.

1.4 Preparation of6-(4-{2-[3-methyl-4-(2-{4-[6-(2-methylacryloyloxy)hexyl]-phenyl}ethyl)phenyl]ethyl}phenyl)hexyl2-methacrylate

600 mg of(6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}-2-methylphenyl)-ethyl]phenyl}hexan-1-olare initially introduced in 15 ml of dichloromethane together with 0.30ml (3.54 mol) of methacrylic acid and 10 mg (0.08 mmol) of DMAP. 3.5 ml(3.5 mmol, 1 M soln. in CH₂Cl₂) of DCC in are metered in, and the batchis stirred for 3 h. 100 mg (0.79 mmol) of oxalic acid dihydrate areadded, and the mixture is filtered. The filtrate is concentrated todryness, and the residue is purified by column chromatography (SiO₂,pentane:MTBE=9:1), giving6-(4-{2-[3-methyl-4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}phenyl)-hexyl2-methyacrylate (1) as a colourless solid having a melting point of 38°C.

Phase sequence: C 38 I

¹H-NMR (400 MHz, CHCl₃): δ=7.15-7.07 (m, 9H, H_(aryl.)), 7.01-6.47 (m,2H, H_(aryl.)), 6.10-6.08 (m, 2H, CMe=CH₂), 5.55-5.53 (m, 2H, CMe=CH₂),4.14 (t, 4H, J=6.7 Hz, 2×-CH₂—OC(O)CMe=CH₂), 2.89-2.79 (m, 8H,H_(benzyl.)), 2.61-2.56 (m, 4H, H_(benzyl.)), 2.28 (s, 3H, Me), 1.95(bs, 6H, Me_(acryl.)), 1.71-1.59 (m, 8H, —CH₂—), 1.46-1.34 (m, 8H,—CH₂—).

MS (EI): m/e (%)=636 (62, M⁺), 69 (100).

EXAMPLE 26-(4-{2-[4-(2-{4-[6-(2-Methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}-phenyl)hexyl2-methacrylate (2)

Compound (2) according to the invention,6-(4-{2-[4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}phenyl)hexyl2-methacrylate, is synthesised analogously to compound (1) from Example1.

6-(4-{2-[4-(2-{4-[6-(2-Methylacryloyloxy)hexyl]phenyl}ethyl)phenyl]ethyl}-phenyl)hexyl2-methacrylate (2) is obtained as a colourless solid having an m.p. of80° C.

Phase sequence: C 80 S_(B) (60) l

¹H-NMR (400 MHz, CHCl₃): δ=7.13-7.06 (m, 12H, H_(aryl.)), 6.09-6.08 (m,2H, CMe=CH₂), 5.55-5.52 (m, 2H, CMe=CH₂), 4.13 (t, 4H, J=6.7 Hz,2×-CH₂—OC(O)CMe=CH₂), 2.87 (s, 8H, H_(benzyl.)), 2.61-2.56 (m, 4H,H_(benzyl.)), 1.95 (bs, 6H, Me_(acryl.)), 1.72-1.57 (m, 8H, —CH₂—),1.46-1.34 (m, 8H, —CH₂—).

MS (EI): m/e (%)=622 (11, M⁺), 104 (100).

EXAMPLE 36-(4-{2-[4-(2-{4-[6-(2-Methylacryloyloxy)hexyl]phenyl}ethyl)naphthalen-1-yl]ethyl}phenyl)hexyl2-methacrylate (3)

Compound (3) according to the invention,6-(4-{2-[4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)naphthalen-1-yl]ethyl}phenyl)hexyl2-methacrylate, is synthesised as described below.

3.1 Preparation of naphthalene-1,4-dicarbaldehyde

80.0 g (0.28 mol) of 1,4-dibromonaphthalene are initially introduced in800 ml of THF at −70° C., and 200 ml (0.32 mmol, 15% soln. in hexane) ofn-BuLi are added. After 1 h, 24 ml (0.31 mol) of DMF are slowly addeddropwise, and the mixture is stirred for 30 min. 500 ml (0.80 mmol, 15%soln. in hexane) of n-BuLi are subsequently metered in, and the mixtureis left at −70° C. for 2 h. 110 ml (1.4 mol) of DMF are added. After 30min., the batch is slowly warmed and hydrolysed using dilutehydrochloric acid. The mixture is extracted a number of times with MTBE,and the combined organic phases are washed with sat. antrium chloridesolution. The solution is dried using sodium sulfate and concentrated todryness. The residue is digested in MTBE and filtered off with suction.

3.2 Preparation of 1,4-bis-[(E,Z)-2-(4-bromophenyl)vinyl]naphthalene

20.0 g (0.11 mol) of naphthalene-1,4-dicarbaldehyde are initiallyintroduced in 500 ml of dichloromethane together with 125.0 g (0.24 mol)of 4-bromobenyzltriphenylphosphonium bromide and 6.50 g (24.6 mmol) of18-crown-6. 30.0 g (0.53 mol) of powdered KOH are added in portions at−70° C. The mixture is stirred at −70° C. for 2 h, and the batch iswarmed to room temperature. After 1 h at this temperature, water isadded, and the organic phase is separated off.

The aqueous phase is extracted with dichloromethane, and the combinedorganic phases are washed with sat. ammonium chloride soln. The solutionis filtered absorptively (SiO₂, CH₂Cl₂), and the filtrate isconcentrated to dryness. The crude product is purified by columnchromatography (SiO₂, toluene:n-heptane=1:1), giving1,4-bis-[(E,Z)-2-(4-bromophenyl)vinyl]naphthalene as a semicrystallinesolid.

3.3 Preparation of6-{4-[(E,Z)-2-(4-{(E,Z)-2-[4-(6-hydroxyhex-1-ynyl)-phenyl]vinyl}naphthalen-1-yl)vinyl]phenyl}hex-5-yn-1-ol

A mixture of 50.0 g (0.1 mol) of1,4-bis-[(E,Z)-2-(4-bromophenyl)vinyl]-naphthalene, 7.3 g (10 mmol) ofbis(triphenylphosphine)palladium(II) chloride, 2.0 mg (11 mmol) ofcopper(I) iodide and 75 ml (0.54 mol) of triethylamine in 300 ml of DMFis warmed to 60° C. 40.0 g (0.41 mol) of 5-hexyn-1-ol dissolved in 400ml of DMF are metered in. When the addition is complete, the batch isstirred at 75° C. for 19 h. After cooling, the mixture is diluted withdichloromethane and neutralised using dil. hydrochloric acid. Theorganic phase is separated off, and the aqueous phase is extracted withdichloromethane. The combined organic phase is washed with sodiumchloride solution and dried using sodium sulfate. The solution isconcentrated to dryness, and the residue is purified by columnchromatography (SiO₂, dichloromethane:MTBE=8:2→1:1).

3.4 Preparation of6-{-4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]phenyl}hexan-1-ol

25.0 g (47.7 mmol) of6-{4-[2-(4-{2-[4-(6-hydroxyhex-1-ynyl)phenyl]vinyl}-naphthalen-1-yl)vinyl]phenyl}hex-5-yn-1-ol(E/Z mixture) are hydrogenated at room temperature for 17 h in thepresence of Pd/C (5% of Pd) in THF. The solution is filtered andconcentrated to dryness. The residue is recrystallised fromn-heptane/MTBE (1:1), giving6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]phenyl}hexan-1-olas a colourless solid.

3.5 Preparation of6-(4-{2-[4-(2-{-4-[6-(2-methylacryloyloxy)hexyl]phenyl}-ethyl)naphthalen-1-yl]ethyl}phenyl)hexyl2-methacrylate

10.0 g (18.6 mmol) of6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]phenyl}hexan-1-olare initially introduced in 100 ml of dichloromethane together with 50ml (0.62 mol) of pyridine and 200 mg (1.64 mmol) of DMAP. 8.0 g (51.6mmol) of methacrylic anhydride in 100 ml of DCM are metered in (icecooling), and the batch is stirred for 19 h. The batch is washed withdil. hydrochloric acid and sat. sodium chloride solution, and theorganic phase is dried using sodium sulfate. The solution isconcentrated to dryness, and the residue is purified by columnchromatography (SiO₂, pentane:DCM=1:1 DCM), giving6-(4-{2-[4-(2-{4-[6-(2-methylacryloyloxy)hexyl]phenyl}ethyl)naphthalen-1-yl]ethyl}-phenyl)hexyl2-methacrylate (3) as a colourless solid having a melting point of 47°C.

Phase sequence: T_(g) −45 C 47 I

¹H-NMR (300 MHz, CHCl₃): δ=8.16-8.11 (m, 2H, H_(aryl.)), 7.56-7.50 (m,2H, H_(aryl.)), 7.24-7.09 (m, 10H, H_(aryl.)), 6.11-6.08 (m, 2H,CMe=CH₂), 5.54-5.52 (m, 2H, CMe=CH₂), 4.14 (t, 4H, J=6.7 Hz,2×-CH₂—OC(O)CMe=CH₂), 3.38-3.31 (m, 4H, H_(aliph.)), 3.05-2.98 (m, 4H,H_(aliph.)), 2.64-2.56 (m, 4H, H_(aliph.)), 1.95 (bs, 6H, Me_(acryl.)),1.73-1.57 (m, 8H, —CH₂—), 1.47-1.33 (m, 8H, —CH₂—).

MS (EI): m/e (%)=673 (100, M⁺).

EXAMPLE 46-{4-[2-(4-{2-[4-(6-Acryloyloxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]-phenyl}hexylacrylate (4)

Compound (4) according to the invention,6-{4-[2-(4-{2-[4-(6-acryloyloxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]phenyl}hexylacrylate, is synthesised analogously to Examples 1 and 3 from6-{4-[2-(4-{2-[4-(6-hydroxyhexyl)phenyl]ethyl}naphthalen-1-yl)ethyl]phenyl}hexan-1-ol(see Example 3, step 3.4).

Phase sequence: T_(g) −47 C 55 I

MS (EI): m/e (%)=644 (83, M⁺), 105 (100).

USE EXAMPLE 1

The following monomers are used:

RM257 has the phase sequence C 66 N 127 I.

RM-CC has the phase sequence C 14 SmB 33 I.

The following additives are used:

(Dp: chiral dopant, In: polymerisation initiator)

TABLE 1 Composition of the base mixture (host) H1 before addition of thepolymerisation components: Composition Component Proportion Acronym % byweight Properties PUQU-3-F 5.00 T(N, I): 66.6° C. AGUQU-3-F 13.00 Δn(20° C., 589 nm): 0.148 AUUQU-2-F 6.00 AUUQU-3-F 10.00 AUUQU-4-F 6.00AUUQU-5-F 9.00 AUUQU-7-F 6.00 AUUQU-3-T 8.00 AUUQU-3-OT 12.00 PUZU-2-F6.00 PUZU-3-F 10.00 PUZU-5-F 9.00 Σ 100.00Description of the Polymerisation

Before the polymerisation of a sample, the phase properties of themedium are established in a test cell having a thickness of about 10microns and an area of 2×2.5 cm². The filling is carried out bycapillary action at a temperature of 75° C. The measurement is carriedout under a polarising microscope with heating stage with a temperaturechange of 1° C./min.

The polymerisation of the media is carried out by irradiation with a UVlamp (Dymax, Bluewave 200, 365 nm interference filter) having aneffective power of about 3.0 mW/cm² for 180 seconds. The polymerisationis carried out directly in the electro-optical test cell.

The polymerisation is carried out initially at a temperature at whichthe medium is in the blue phase I (BP-I). The polymerisation is carriedout in a plurality of part-steps, which gradually result in completepolymerisation. The temperature range of the blue phase generallychanges during the polymerisation. The temperature is therefore adaptedbetween each part-step so that the medium is still in the blue phase. Inpractice, this can be carried out by observing the sample under thepolarising microscope after each irradiation operation of about 5 s orlonger. If the sample becomes darker, this indicates a transition intothe isotropic phase. The temperature for the next part-step is reducedcorrespondingly.

The entire irradiation time which results in maximum stabilisation istypically 180 s at the irradiation power indicated. Furtherpolymerisations can be carried out in accordance with an optimisedirradiation/temperature programme.

Alternatively, the polymerisation can also be carried out in a singleirradiation step, in particular broad if a blue phase is already presentbefore the polymerisation.

Electro-Optical Characterisation

After the above-described polymerisation and stabilisation of the bluephase, the phase width of the blue phase is determined. Theelectro-optical characterisation is carried out subsequently at varioustemperatures within and if desired also outside this range. The testcells used are fitted on one side with interdigital electrodes on thecell surface. The cell gap, the electrode separation and the electrodewidth are typically each 10 microns. This uniform dimension is referredto below as the gap width. The area covered by electrodes is about 0.4cm². The test cells do not have an alignment layer.

For the electro-optical characterisation, the cell is located betweencrossed polarising filters, where the longitudinal direction of theelectrodes adopts an angle of 45° to the axes of the polarising filter.The measurement is carried out using a DMS301 (Autronic-Melchers) at aright angle to the cell plane, or by means of a highly sensitive cameraon the polarising microscope. In the voltage-free state, the arrangementdescribed gives an essentially dark image (definition 0% transmission).

Firstly, the characteristic operating voltages and then the responsetimes are measured on the test cell. The operating voltage is applied tothe cell electrodes in the form of rectangular voltage having analternating sign (frequency 100 Hz) and variable amplitude, as describedbelow.

The transmission is measured while the operating voltage is increased.The reaching of the maximum value of the transmission defines thecharacteristic quantity of the operating voltage V₁₀₀. Equally, thecharacteristic voltage V₁₀ is determined at 10% of the maximumtransmission. These values are measured at various temperatures in therange of the blue phase.

Relatively high characteristic operating voltages V₁₀₀ are observed atthe upper and lower end of the temperature range of the blue phase. Inthe region of the minimum operating voltage, V₁₀₀ generally onlyincreases slowly with temperature. This temperature range, limited by T₁and T₂, is referred to as the usable, flat temperature range (FR). Thewidth of this “flat range” (FR) is (T₂−T₁) and is known as the width ofthe flat range (WFR).

The precise values of T₁ and T₂ are determined by the intersections oftangents on the flat curve section FR and the adjacent steep curvesections in the V₁₀₀/temperature diagram.

In the second part of the measurement, the response times duringswitching on and off (τ_(on), τ_(off)) are determined. The response timeτ_(on) is defined by the time to achievement of 90% intensity afterapplication of a voltage at the level of V₁₀₀ at the selectedtemperature. The response time τ_(off) is defined by the time until thedecrease by 90% starting from maximum intensity at V₁₀₀ after reductionof the voltage to 0 V. The response time is also determined at varioustemperatures in the range of the blue phase.

As further characterisation, the transmission at continuously increasingand falling operating voltage between 0 V and V₁₀₀ is measured at atemperature within the FR. The difference between the two curves isknown as hysteresis. The difference in the transmissions at 0.5·V₁₀₀ andthe difference in the voltages at 50% transmission are, for example,characteristic hysteresis values and are known as ΔT₅₀ and ΔV₅₀respectively. Furthermore, the contrast during the first switching-onand during the subsequent switching off is distinguished as the ratio ofthe respective maximum and minimum transmission.

USE EXAMPLES M1 TO M Use Example Mixture M1 and Comparative Examples C1and C2

Proportion [% by weight] Component M1 C1 C2 H1 85.0 85.0 86.3 Dp  3.8 3.8  2.5 In  0.2  0.2  0.2 (1)  6.0 — — RM257 —  5.0  5.0 RM-CC  5.0 6.0  6.0

The media are characterised as described before the polymerisation. TheRM components are then polymerised by single irradiation (180 s) in theblue phase, and the media obtained are re-characterised.

Measurement values M1 C1 C2 Transition point before 44.1 49.5 thepolymerisation Temperature range of — — — the blue phase V₁₀ (20° C.)34.9 V 25.7 V 22.2 V₁₀₀ (20° C.) 78.0 V 64.0 V 55.0 V ΔV₅₀ (20° C.) 4.2V 6.2 V  4.2 Contrast, switching on 569 503 45.0 Contrast, switching off543 32 50.1 Gap width 10 μm 10 μm 10 μm

The polymer-stabilised medium M1, prepared using monomer (1) accordingto the invention, exhibits a reduction in hysteresis (ΔV₅₀) and asignificant increase in the contrast during switching on and offcompared with the polymer-stabilised medium C1, prepared using monomerRM257 from the prior art. Furthermore, it is evident that the contrastduring switching off in the case of the polymer-stabilised medium C1 ismuch lower than during switching on. In the case of mixture C2, which isanalogous to mixture C1, but comprises less chiral dopant, the contrastduring switching on and off is very similar. The lower contrast comparedwith M1 and C1 is therefore due to the fact that a visible blue phase ispresent in the case of C2. This means that the monomer mixture presentedin this invention is particularly suitable for the stabilisation of bluephases with a high concentration of chiral dopant.

The invention claimed is:
 1. A liquid crystal display containing one ormore compounds of the formula IP^(a)-(Sp^(a))_(s1)-A²-CH₂CH₂-A¹-CH₂CH₂-A³-(Sp^(b))_(s2)-P^(b)  I inwhich the individual radicals have the following meaning P^(a) P^(b)each, independently of one another, denote a polymerisable group,Sp^(a), Sp^(b) on each occurrence, identically or differently, denote aspacer group, s1, s2 each, independently of one another, denote 0 or 1,A¹, A², A³ each, independently of one another, denote a radical selectedfrom the following groups a) the group consisting oftrans-1,4-cyclohexylene, 1,4-cyclohexenylene and 4,4′-bicyclohexylene,wherein one or more non-adjacent CH₂ groups may be replaced by —O—and/or —S—, and wherein, one or more H atoms may be replaced by F, b)the group consisting of 1,4-phenylene wherein one or two CH groups maybe replaced by N wherein one of more H atoms are replaced by L and1,3-phenylene, wherein one or two CH groups may be replaced by N andwherein, one or more H atoms may be replaced by L, c) the groupconsisting of tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl,tetrahydrofuran-2,5-diyl, cyclobut-1,3-diyl, piperidine-1,4-diyl,thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may be mono-or polysubstituted by L, d) the group consisting of saturated, partiallyunsaturated or fully unsaturated, and optionally substituted, polycyclicradicals having 5 to 20 cyclic C atoms, one or more of which may also bereplaced by heteroatoms, selected from the group consisting ofbicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]-octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl,

wherein one or more H atoms in these radicals may be replaced by L,and/or one or more double bonds may be replaced by single bonds, and/orone or more CH groups may be replaced by N, L on each occurrence,identically or differently, denotes, F, Cl, CN, SCN, SF₅ orstraight-chain or branched, in each case optionally fluorinated alkyl,alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy oralkoxycarbonyloxy having 1 to 12 C atoms, R⁰, R⁰⁰ each, independently ofone another, denote H, F or straight-chain or branched alkyl having 1 to12 C atoms, wherein, one or more H atoms may be replaced by F, M denotes—O—, —S—, —CH₂—, —CHY— or —CY¹Y²—, Y and Y¹ each, independently of oneanother, have one of the meanings indicated above for R⁰, or denote Clor CN, or a polymer obtainable by polymerisation of one or morecompounds of the formula I and wherein the liquid crystal displayexhibits a blue phase.
 2. A liquid-crystal (LC) medium comprising one ormore compounds of formula I, and optionally additionally one or morepolymerisable compounds and/or one or more liquid-crystalline compounds,or comprising a polymer obtainable by polymerisation of one or morecompounds according to formula IP^(a)-(Sp^(a))_(s1)-A²-CH₂CH₂-A¹-CH₂CH₂-A³-(Sp^(b))_(s2)-P^(b)  I inwhich the individual radicals have the following meaning P^(a) P^(b)each, independently of one another, denote a polymerisable group,Sp^(a), Sp^(b) on each occurrence, identically or differently, denote aspacer group, s1, s2 each, independently of one another, denote 0 or 1,A¹, A², A³ each, independently of one another, denote a radical selectedfrom the following groups a) the group consisting oftrans-1,4-cyclohexylene, 1,4-cyclohexenylene and 4,4′-bicyclohexylene,wherein one or more non-adjacent CH₂ groups may be replaced by —O—and/or —S— and wherein one or more H atoms may be replaced by F, b) thegroup consisting of 1,4-phenylene wherein one or two CH groups may bereplaced by N in which one of more H atoms are replaced by L, and1,3-phenylene, wherein one or two CH groups may be replaced by N andwherein one or more H atoms may be replaced by L, c) the groupconsisting of tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl,tetrahydrofuran-2,5-diyl, cyclobut-1,3-diyl, piperidine-1,4-diyl,thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may, be mono-or polysubstituted by L, d) the group consisting of saturated, partiallyunsaturated or fully unsaturated, and optionally substituted, polycyclicradicals having 5 to 20 cyclic C atoms, one or more of which may also bereplaced by heteroatoms, selected from the group consisting ofbicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]-octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl,

wherein one or more H atoms in these radicals may be replaced by L,and/or one or more double bonds may be replaced by single bonds, and/orone or more CH groups may be replaced by N, L on each occurrence,identically or differently, denotes, F, Cl, CN, SCN, SF₅ orstraight-chain or branched, in each case optionally fluorinated alkyl,alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy oralkoxycarbonyloxy having 1 to 12 C atoms, R⁰, R⁰⁰ each, independently ofone another, denote H, F or straight-chain or branched alkyl having 1 to12 C atoms, wherein one or more H atoms may be replaced by F, M denotes—O—, —S—, —CH₂—, —CHY— or —CY¹Y²—, Y and Y¹ each, independently of oneanother, have one of the meanings indicated above for R⁰, or denote Clor CN, and wherein the medium exhibits a blue phase.
 3. LC mediumaccording to claim 2, characterised in that it comprises the followingcomponents a polymerisable component A comprising one or more compoundsaccording to formula I, and a liquid-crystalline component B comprisingone or more compounds of the formula II

in which the individual radicals have the following meaning R²² denotesH, F, Cl, CN, NCS, SF₅, SO₂CF₃ or straight-chain or branched alkylhaving 1 to 20 C atoms, which is unsubstituted or mono- orpolysubstituted by F, Cl or CN, and wherein one or more non-adjacent CH₂groups may also each be replaced, independently of one another, by —O—,—S—, —NH—, —NR⁰¹—, —SiR⁰¹R⁰²—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—,—CO—S—, —CY⁰¹═CY⁰¹— or —C≡C— in such a way that O and/or S atoms are notlinked directly to one another, Y⁰¹, Y⁰² each, independently of oneanother, denote F, Cl or CN, the radicals Y⁰¹ and Y⁰² also denote H,R⁰¹, R⁰² each, independently of one another, denote H or alkyl having 1to 12 C atoms, A²¹, A²², A²³ each, independently of one another and oneach occurrence identically or differently denote

Z²¹, Z²² each, independently of one another and on each occurrenceidentically or differently, denote a single bond, —(CH₂)₄)—, —CH₂CH₂—,—CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CH═CH—, —CF═CF—, —CF═CH—, —(CH₂)₃O—,—O(CH₂)₃—, —CH═CF—, —C≡C—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CO—O— or—O—CO—, X²² denotes F, Cl, —CN, —NCS, —SF₅, —SO₂CF₃, or alkyl, alkenyl,alkenyloxy, alkylalkoxy or alkoxy having 1 to 3 C atoms, which is mono-or polysubstituted by F, Cl or CN, L²¹, L²² each independently of oneanother, denote H or F, m denotes 0, 1 or 2, n denotes 0, 1, 2 or 3, odenotes 0, 1 or 2, where m+n+o denotes 0, 1, 2 or 3, optionally aliquid-crystalline component C comprising one or more compounds of theformula III

in which a, b, c, d each, independently of one another, denote 0, 1 or2, where a+b+c+d is 0, 1, 2, 3 or 4, A³¹, A³², A³³, A³⁴ each,independently of one another and on each occurrence identically ordifferently, denote

Z³¹, Z³², Z³³, Z³⁴ each, independently of one another and on eachoccurrence identically or differently, denote a single bond, —(CH₂)—,—CH₂CH₂—, —CF₂—CF₂—, —CF₂—CH₂—, —CH₂—CF₂—, —CH═CH—, —CF═CF—, —CF═CH—,—(CH₂)₃O—, —O(CH₂)₃—, —CH═CF—, —C≡C—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—,—CO—O— or —O—CO—, R³³ denotes alkyl or alkoxy having 1 to 15 C atoms,which is unsubstituted or mono- or polysubstituted by F, Cl or CN, andwherein one or more non-adjacent CH₂ groups may also each be replaced,independently of one another, by —O—, —S—, —SiR^(x)R^(y)—, —CH═CH—,—C≡C—, —CO—O— and/or —O—CO— in such a way that O and/or S atoms are notlinked directly to one another, L³¹, L³², L³³, L³⁴ each, independentlyof one another, denote H, F, Cl, CN or alkyl or alkoxy having 1 to 15 Catoms, which is unsubstituted or mono- or polysubstituted by F, Cl or CNand wherein one or more non-adjacent CH₂ groups may also each bereplaced, independently of one another, by —O—, —S—, —SiR^(x)R^(y)—,—CH═CH—, —C≡C—, —CO—O— and/or —O—CO— in such a way that O and/or S atomsare not linked directly to one another, with the proviso that at leastone of the radicals L³¹, L³², L³³ and L³⁴ is other than H, X³³ denotesF, Cl, CF₃, OCF₃, CN, NCS, —SF₅ or —SO₂—R^(z), R^(x) and R^(y) each,independently of one another, denote H, alkyl or alkoxy having 1 to 7 Catoms, and R^(z) denotes alkyl having 1 to 7 C atoms, which isunsubstituted or mono- or polysubstituted by F or Cl, and a component Dcomprising one or more optically active and/or chiral compounds.
 4. LCmedium according to claim 3, characterised in that it additionallycomprises one or more compounds selected from the formulae Z, Q1 and Q2

in which R^(z) has one of the meanings indicated for R²² in formula II,

 denotes

X^(Z) denotes F, Cl, CN, NCS, OCF₃, CF₃ or SF₅, R^(Q) has one of themeanings indicated for R²² in formula II, X^(Q) has one of the meaningsindicated for X^(E) in formula E, (F) denotes F or H, and n and m each,independently of one another, denote 0 or
 1. 5. Process for thepreparation of an LC medium ng to claim 2, in which one or moreliquid-crystalline compounds are mixed with one or more compoundsaccording to formula I and optionally with further liquid-crystallinecompounds and/or additives.
 6. LC display containing an LC mediumaccording to claim
 2. 7. LC display according to claim 6, characterisedin that it is a PS or PSA display, a display having a blue phase, aPSA-VA, PSA-OCB, PSA-IPS, PSA-FFS or PSA-TN display.
 8. LC displayaccording to claim 6, comprising an LC cell having two substrates andtwo electrodes, where at least one substrate is transparent to light andat least one substrate has one or two electrodes, and a layer, locatedbetween the substrates, of an LC medium comprising a polymerisedcomponent and a low-molecular-weight component, where the polymerisedcomponent is obtainable by polymerisation of one or more polymerisablecompounds between the substrates of the LC cell in the LC medium. 9.Process for the production of an LC display according to claim 8 inwhich said LC medium is introduced into an LC cell having two substratesand two electrodes, and polymerising the polymerisable compounds,optionally with application of an electrical voltage to the electrodes.10. LC display according to claim 1, characterised in that it is a PS orPSA display, a display having a blue phase, a PSA-VA, PSA-OCB, PSA-IPS,PSA-FFS or PSA-TN display.
 11. A method of producing an image comprisingoperating a liquid crystal display of claim
 1. 12. A method of claim 11characterized in that the display is a PS or PSA display, a displayhaving a blue phase, a PSA-VA, PSA-OCB, PSA-IPS, PSA-FFS or PSA-TNdisplay.
 13. The liquid crystal display of claim 1 wherein, A¹ isselected from a group consisting of:


14. The liquid crystal medium of claim 2 wherein, A¹ is selected from agroup consisting of:


15. The liquid crystal display of claim 1 wherein Y and Y¹ are selectedfrom the group consisting of H, F, Cl, CN, OCF3 and CF3.
 16. The liquidcrystal medium of claim 2 wherein Y and Y¹ are selected from the groupconsisting of H, F, Cl, CN, OCF3 and CF3.
 17. The liquid crystal mediumof claim 3 wherein m+n+o is 0, 1 or
 2. 18. The liquid crystal medium ofclaim 3 wherein the one or more non-adjacent CH2 groups may also each bereplaced, independently of one another, by a straight-chain alkyl,alkoxy, alkenyl, alkenyloxy or —O-alkylene-O— radical having up to 10 Catoms, which is unsubstituted or mono- or polysubstituted by F or Cl.19. The liquid crystal medium of claim 3 wherein R^(x) and R^(y) ismethyl, ethyl, propyl or butyl.
 20. The liquid crystal medium of claim 3wherein R^(z) is alkyl having 1 to 7 C atoms, which is unsubstituted ormono- or polysubstituted by CF₃, C₂F₅ or n-C₄F₉.
 21. LC display of claim8 wherein the where the polymerised component is obtainable bypolymerisation of one or more polymerisable compounds between thesubstrates of the LC cell in the LC medium with the application of anelectrical voltage to the electrodes, wherein at least one of thepolymerisable compounds is a compound according to formula I.